Hey everyone!
Today we’re diving into something small but mighty—modal verbs. Those little words like can, could, may, might, must, shall, should, will, would.
Why are they such a big deal? Because they can completely change what you think someone means. And trust me, misunderstandings can get messy.
Imagine this: You’re texting someone you like. They say, “I might see you tonight.” You start getting ready, pick your best outfit, cancel other plans. Hours later—nothing. No call. No text. You feel betrayed, like they lied. But guess what? They didn’t lie. You just didn’t know what might really means. (Hint: it’s not a pinky promise.)
Now, here’s another one: Your boss says, “I would like this report done soon.” And you think, “Aw, how nice, they’re just sharing their feelings about reports.” Nope. That’s not a confession—it’s an order wearing a polite disguise.
See what’s going on? Modal verbs don’t just talk about actions. They show how sure someone is, how polite they want to sound, or whether something is possible, necessary, or allowed. They reveal attitude. And if you miss that? You could end up waiting all night for a date that never comes—or unemployed.
That’s why learning modal verbs is so important. They help you:
✔ Say how certain you are.
✔ Show obligation or permission.
✔ Sound polite without sounding like a robot.
So today, we’re going to unlock the secret power of modals—so you never confuse might with will again, and never mistake a boss’s request for a friendly suggestion.
Ready? Let’s dive in.
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Think about this: modal verbs allow you to talk about what you think about the fact, not just the fact itself. For example:
This is the fastest way to Hollywood.
That’s either true or false. But if you use modal verbs:
This must be the fastest way to Hollywood.
This could be the fastest way to Hollywood.
Now, you are not stating a fact. You are expressing your belief or attitude about the fact.
Do you see how useful modal verbs are? They make your English sound more natural, polite, and nuanced.
Today, we will learn how to use modal verbs correctly. But first, let’s start with this question: What are modal verbs?
The core modal auxiliary verbs in English are: can, could, may, might, must, shall, should, will, would, ought to.
They share several important grammatical characteristics:
Always Followed by the Bare Infinitive: Modals are always followed by the base form of the main verb (the bare infinitive, without "to").
Correct: "You must study." (Not "You must to study.")
Correct: "She can swim." (Not "She can swims.")
Never Change Form: Modal verbs themselves never change their form for person or number (e.g., no -s for third-person singular).
No "To" Infinitive: Unlike other auxiliaries, they are not followed by "to" (except for ought to).
Used with "Not" for Negation: They form negatives by simply adding "not" after the modal.
Examples: cannot, should not, will not.
Inversion for Questions: They form questions by inverting with the subject.
Examples: "Can you help me?", "Will she come?"
A key feature of modal verbs is that they often have more than one meaning, and the same meaning can sometimes be expressed by different modal verbs. The interpretation of a particular modal verb heavily depends on the context in which it is used.
For instance, consider the sentence: "You must study hard."
In the context: "To pass the test, you must study hard."
Here, "must" expresses an obligation or a strong necessity.
In the context: "You must study hard since you get all A's."
Here, "must" expresses a logical deduction or strong belief about a situation.
As these examples signify, the meanings of modal verbs can broadly be grouped into two fundamental categories:
Epistemic Modality: This indicates the assuredness or certainty of the speaker's belief about a given situation or proposition. It's about how certain the speaker believes something is or is likely to be.
Deontic Modality: This indicates obligation, permission, necessity, or duty. It's about how necessary an action needs to be done or whether it is allowed.
Sometimes, it can be ambiguous whether the modal verb in a sentence is used for epistemic or deontic purposes. For instance, "You must be at home" could mean either:
"You are obligated to be at home." (Deontic)
"I am certain that you are at home." (Epistemic) The surrounding context is the only clue to determine the intended meaning.
In general, the degrees of the two attitudes correspond: modal auxiliary verbs that indicate strong epistemic certainty also tend to indicate strong deontic obligation, and those weak in one are weak in the other.
Deontic Modality: Obligation, Permission, and Ability
Deontic modality deals with duty, obligation, permission, and ability. Different modal verbs express different degrees of these concepts.
Strong Obligation/Necessity: must, have to, ought to, should (stronger advice/expectation)
"You must clean the room." (Strong duty, usually imposed externally)
"I have to do it." (Strong obligation, often from a rule or circumstance)
"I ought to apologize." (Strong moral obligation or correct action)
"I should finish this report by tomorrow." (Strong advice or expectation, but less forceful than must/have to)
Permission/Ability: can, may, could
"You can leave now." (Giving permission, or stating ability)
"May I go to the bathroom?" (Asking permission, more formal than can)
"I can do it." (Stating ability)
Weak/Almost No Commitment: could, might
"You could clean the room." (Very weak suggestion or possibility, implying weak duty or effort)
"I could do it." (Indicates ability but with no commitment to act)
"I might do it." (Indicates a very weak possibility of action, showing almost no commitment)
Deontic modality ranking
Let’s imagine these modal verbs as characters in a grand “Deontic Modality League,” each with their own personality and level of authority.
At the top of the hierarchy, we have Must, the Lawmaker. Must is absolute authority—the ultimate enforcer. When Must speaks, there’s no room for negotiation. For example, if I say, “You must submit your report by 5 PM,” it’s not a suggestion—it’s a command. Must’s catchphrase? “No choice, my word is law!”
Next comes Shall, the Formal Commander. Shall carries high authority, often in legal or official contexts. It’s still strong, but it’s more formal than Must. You might hear, “Members shall follow the code of conduct.” Shall’s authority is serious, but it comes with a polished, official tone: “I sound official, so obey!”
Then we meet Will, the Promiser. Will isn’t about rules or laws—it’s about personal commitment and determination. When someone says, “I will finish this project today,” they’re expressing intention and resolve. Will’s motto? “I’m determined, and I keep my word!”
Moving down a notch in authority, we have Should and Ought to, the Advisors. These modals aren’t commands—they’re strong recommendations. They suggest what is wise or expected without enforcing it. For example, “You should exercise daily.” Their attitude is gentle yet firm: “I’m not your boss, but trust me!”
Next is May, the Gatekeeper. May is polite, granting permission rather than issuing orders. If I say, “You may enter the hall,” I’m allowing you to act, but the power still rests with me. May’s catchphrase reflects its polite authority: “You shall pass… if I allow it.”
Then comes Can, the Practical Authority. Can is informal and flexible, often used for everyday permission or ability. For instance, “You can take a break now.” Can is pragmatic, saying, “If it’s possible, I decide if you do it.”
Following Can is Could, the Polite Permitter. Could is softer and tentative, often used for polite suggestions or hypothetical possibilities. For example, “You could join us later.” Could isn’t pushing—it’s offering: “I’m just suggesting, no pressure.”
Finally, at the lowest end of the hierarchy, we have Might, the Hesitant Hero. Might is cautious and weak in authority, often expressing a tentative possibility or gentle suggestion. For example, “You might want to check the instructions first.” Might admits uncertainty: “I’m not sure, but it could be an option…”
So, if we rank the Deontic Modality League by strength of obligation and authority, the order goes like this:
Must > Shall > Will > Should/Ought to > May > Can > Could > Might
Each character plays a role in how we communicate duty, permission, and advice in English, giving color and nuance to our language. Understanding them helps you not only interpret others’ speech accurately but also wield your own words with the right level of force or politeness.
Epistemic Modality: Certainty and Possibility
Epistemic modality reflects how sure the speaker is about the truth or likelihood of a given situation. Different modal verbs convey varying degrees of this assuredness.
Strong Assuredness/Logical Deduction: will, must, should, ought to
"Will" is generally used for strong predictions or certainties about the future based on present information.
"The winner will be John." (Strong prediction)
"Must" implies a very strong belief or logical necessity based on evidence.
"You must be starving." (Strong belief based on observation, e.g., 'You haven't eaten all day.')
"Should" and "ought to" convey a strong expectation or high probability, implying something is very likely to be true.
"The winner should (or ought to) be John." (Strong expectation based on knowledge)
Weak Assuredness/Possibility: can, could, may, might These modals express varying degrees of possibility, with might often indicating the weakest. Depending on stress and context, their specific nuances of sureness can shift.
"Can" often implies possibility or a general truth, sometimes about capability.
"That can be true." (It is possible for it to be true.)
"You can be starving (if you haven't eaten all day)." (It is possible/understandable to be starving.)
"Could" suggests a weaker or more hypothetical possibility than can.
"The winner could be John." (One of several possibilities.)
"May" indicates possibility, slightly stronger than might.
"It may snow tonight." (There is a possibility of snow.)
"Might" indicates the weakest degree of possibility.
"The winner might be John." (A very small chance.)
"You might be starving." (Weak belief, less certain than 'can' or 'must'.)
"May" vs. "Might/Could" in American English
In American English, there is an important difference in informal speech.
In everyday conversations, Americans usually use might or could to talk about possibility, not may.
He might come to the party.
He could come to the party.
Both mean that it is possible. If you say: He may come to the party in an informal conversation, many Americans will think you are talking about permission—like “It is allowed for him to come.”
But in formal English, like in news reports or official statements, may is often used for possibility.
The protesters may strike on Friday.
(Meaning: It is possible that they will strike.)
Epistemic modality ranking
Here’s a mini ranking chart for epistemic modality (certainty and possibility) in English, from strongest certainty to weakest:
Must → Logical necessity; almost 100% sure based on evidence.
Example: He must be at home. (I see his car outside.)Will → Strong prediction or assumption about the future.
Example: She will pass the exam. (I’m very confident.)Should / Ought to → High probability, strong expectation.
Example: They should arrive by 6 p.m.Can/may (formal) → General or realistic possibility; strong ability.
Example: It can get very cold in winter.
Example: It may happen
Could/might → Tentative possibility
Example: It could rain later. (less certain)
Example: He might join us later.
Would → Usually for hypothetical or imagined situations, not real certainty.
Example: I would help if I had time.
Negative modality
As we saw earlier, modal auxiliary verbs can be ranked according to their strength in both deontic and epistemic meanings. Now, let’s explore what happens when we add “not.” This is where the power shifts, and negative modals often behave in ways you might not expect. They do not simply reverse the positive meaning; instead, they take on new roles, and it helps to think of them along a spectrum from the strongest “no” to the softest “maybe not.”
Let’s start with must not. In its positive form, “must” expresses strong duty or certainty, as in “You must submit your report by five o’clock.” It signals an obligation that is non-negotiable. But when we add “not,” “must not” no longer means “no duty”; instead, it communicates prohibition. For example, “You must not eat this” carries a clear sense of something being absolutely forbidden. In contrast, the true opposite of “must" in a deontic sense is phrases like “don’t have to” or “don’t need to,” which signal the absence of obligation rather than prohibition. So if we say, “He doesn’t have to get up early,” we are indicating that it is optional—he may, but he is not required to.
In epistemic terms, “must” expresses logical certainty. Its negative counterpart is “cannot,” which expresses logical impossibility. For example, “John must be at home” shows a strong positive deduction, while “John cannot be at home” conveys strong negative deduction. Notice how negation completely changes the force of the statement.
Next, we have should not or ought not to. Both “should” and “ought to” offer advice or express expectations. When negated, they do not impose prohibition but instead provide negative advice. For instance, “You shouldn’t skip breakfast,” “He shouldn’t be late,” or “You ought not to lie” all function as cautions or warnings rather than commands. They are softer than “must not,” guiding action rather than forbidding it.
Moving on, may not carries a dual meaning. In its positive form, “may” grants permission or expresses possibility. When negative, “may not” can either politely deny permission, as in “You may not enter,” or express uncertainty about a future event, like “It may not rain tomorrow.”.
Then we come to cannot. While “can” expresses ability or informal permission, the negative “cannot" indicate prohibition, inability, or impossibility. For example, “You cannot park here” forbids action, “I cannot do this” signals a lack of ability, and “It cannot be true” expresses impossibility. In epistemic usage, “cannot” serves as the logical opposite of must, reinforcing how context shifts meaning.
Could not is generally used for past ability or hypothetical possibility. It primarily indicates past impossibility or inability: “He couldn’t finish the race” or “It couldn’t have been her.” In hypothetical contexts, “could not” can express present or future impossibility, as in “I could not do that to my best friend” or “I couldn’t live without coffee.” When talking about present impossibility with certainty, however, we default to “cannot”: “I cannot believe this news.”
Finally, might not. “Might” often overlaps with “could" in expressing possibility. While “It could rain tomorrow” and “It might rain tomorrow” sound similar in the positive, their negative forms diverge. “Could not” refers to past impossibility or inability, whereas “might not” conveys uncertain future possibility—it does not imply impossibility. For example, “He might not come to the party,” “It might not rain tomorrow,” or “We might not finish on time” all show a chance that something will not happen. You can think of “could not” as a detective of the past and “might not” as a hesitant doubter of the future.
When we use negative modals, their ranking depends on whether they express deontic meaning (rules, permission, advice) or epistemic meaning (certainty about truth). The order of strength changes between these two functions.
Deontic Meaning Ranking
In the deontic sense, we are talking about rules, duties, or advice. The scale goes from the strictest prohibition to the softest suggestion.
Must not. At the top, we have ‘must not,’ which signals an absolute rule—there is no room for negotiation. If you say “You must not enter this room,” it means it is strictly forbidden.
Cannot. Next comes ‘cannot’ (or can’t). This also expresses strong prohibition, but frames it as an impossibility or a rule, for example, “You cannot park here.”
May not. Softer than that is may not, which sounds formal and polite when denying permission: “You may not borrow this book.” It’s still a prohibition, but less forceful than must not.
Should not. ought not to. Moving further down, we find ‘should not’ (or ought not to). These do not sound like prohibitions at all, but rather advice or guidance: “You shouldn’t skip breakfast.”
would not. Finally, at the weakest end, there is “would not,” which is not about obligation at all but about personal stance or conditional advice, as in: “I would not park here if I were you.”
Notice that could not and might not do not appear in this scale—they are not about duties or permissions, so they don’t belong to the deontic ranking.
Epistemic Meaning Ranking
Now, let’s switch to epistemic meaning, where modals express degrees of certainty about whether something is true or not. Here the scale runs from strong impossibility to weak, tentative doubt.
Cannot. The strongest is cannot (or can’t)—when you use it epistemically, you are saying something is impossible, for example: “He cannot be at home.” That means you are 100% sure it is not true.
Could not. Next comes could not, which signals a past or hypothetical impossibility, as in “He couldn’t have been at home.”
Should not. Weaker still is should not (or ought not to) when used epistemically. Here it means you don’t expect something to happen, though it’s still possible: “They shouldn’t be late.”
May not. Below that is may not, which expresses uncertainty: “It may not rain tomorrow.” You are admitting the possibility that something won’t happen.
Might not. At the very weakest end is might not, which signals a tentative maybe-not: “He might not come to the party.”
Importantly, must not and would not are not epistemic in modern English. Must not belongs only to the deontic scale (prohibition), not to certainty. Would not expresses refusal or insistence, not a degree of likelihood.
Today, we focused on how modal verbs change the meanings of sentences by signaling the writer’s attitude. In our next lecture, we’ll explore how to use modal verbs to talk about past situations.