Modal Verbs
Modal verbs (can, could, may, might, must, should, etc.) sit directly before the base form of another verb — no "to", no -s — and each one signals a specific shade of meaning, such as ability, permission, possibility, obligation, or advice, that depends on context rather than a fixed rule.
Formula
Examples
Usage
- •Ability (can), possibility (may/might), necessity (must), advice (should)
- •Expressing obligation, permission, and possibility
- •Making polite requests and offers
What are modal verbs used for?
Modal verbs express ability (can, could), permission (can, may), possibility (may, might, could), necessity or obligation (must, have to), and advice (should). The same modal often covers more than one meaning — "can" alone handles ability (I can swim), permission (Can I leave?), and even possibility in some contexts.
They're also the standard way to make polite requests and offers: Could you help me? is softer than a plain imperative, and Would you like some tea? functions as an offer rather than a real question.
Must or have to — what's the difference?
"Must" expresses the speaker's own sense of obligation: I must call my mother (I feel I should). "Have to" expresses an obligation that comes from outside — a rule, a law, someone else's authority: I have to wear a uniform at work.
In everyday British English this distinction is fading — "have to" increasingly covers both cases — but it's still a real distinction learners are expected to know at B1.
Mustn't or don't have to — what's the difference?
These look like a matching negative pair but mean opposite things. "Mustn't" means prohibition — you are not allowed to: You mustn't park here (it's forbidden). "Don't have to" means no obligation — it's your choice: You don't have to come (you can if you want, but nothing requires it).
This is one of the most common false-friend errors at this level, since many languages use a single negative form for both meanings.
Comparison Table
| Form | Meaning | Common modals | Example |
|---|---|---|---|
| Ability | can, could | I can speak three languages. | |
| Permission | can, may, could | Could I borrow your pen? | |
| Possibility | may, might, could | It might snow tomorrow. | |
| Obligation / necessity | must, have to | You must wear a seatbelt. | |
| Advice | should | You should see a doctor. |
Save this comparison chart
More Examples
You must wear a seatbelt.
Strong obligation (rule)
She may leave early today.
Permission granted
It might snow tomorrow.
Weak possibility about the future
You should see a doctor.
Advice / recommendation
Could I borrow your pen?
Polite request
Common Mistakes
- ✗Using "must" for deduction in negative: "He mustn't be home" (prohibition) vs "He can't be home" (deduction).
- ✗Modals don't take -s or infinitive "to": "She musts go" and "She must to go" are both wrong.
Tips
- ✓"Must" expresses personal obligation; "have to" expresses external obligation.
- ✓"May" is more formal than "might" for possibility.
Modal Verbs Quick Reference
Meaning, negative form, and examples for every modal
Ability
can
Positive meaning
present ability
Negative form + meaning
can't — impossibility / prohibition
Example
She can speak three languages.
You can't park here.
could
Positive meaning
past ability / polite ask
Negative form + meaning
couldn't — past impossibility
Example
He could run fast when he was young.
I couldn't find my keys.
Permission
can
Positive meaning
informal permission
Negative form + meaning
can't — refusal of permission
Example
Can I use your phone?
You can't come in.
may
Positive meaning
formal permission
Negative form + meaning
may not — formal refusal
Example
May I leave early?
You may not enter.
could
Positive meaning
polite request
Negative form + meaning
—
Example
Could you open the window?
Possibility
may
Positive meaning
real possibility (~50%)
Negative form + meaning
may not — possible non-occurrence
Example
It may snow tonight.
It may not be true.
might
Positive meaning
weak possibility (~30%)
Negative form + meaning
might not — weak non-occurrence
Example
She might come to the party.
He might not agree.
could
Positive meaning
theoretical possibility
Negative form + meaning
—
Example
That could be dangerous.
Obligation & Necessity
must
Positive meaning
strong personal obligation
Negative form + meaning
mustn't — prohibition (NOT no obligation)
Example
You must wear a seatbelt.
You mustn't smoke here.
have to
Positive meaning
external obligation
Negative form + meaning
don't have to — no obligation
Example
I have to finish this report.
You don't have to come.
need to
Positive meaning
necessity
Negative form + meaning
needn't / don't need to — unnecessary
Example
You need to see a doctor.
You needn't bring food.
Advice & Recommendation
should
Positive meaning
advice / moral duty
Negative form + meaning
shouldn't — inadvisable
Example
You should get more sleep.
You shouldn't eat so much sugar.
ought to
Positive meaning
moral obligation
Negative form + meaning
ought not to
Example
You ought to apologise.
You ought not to lie.
Future & Prediction
will
Positive meaning
prediction / promise / offer
Negative form + meaning
won't — refusal / negative prediction
Example
It will rain tomorrow.
I won't tell anyone.
shall
Positive meaning
offer / suggestion (BrE)
Negative form + meaning
—
Example
Shall I carry that for you?
would
Positive meaning
conditional / polite request
Negative form + meaning
wouldn't — conditional negative
Example
Would you like some tea?
She wouldn't agree.
| Modal | Positive meaning | Negative form + meaning | |
|---|---|---|---|
| Ability | |||
| can | present ability | can't — impossibility / prohibition | |
| could | past ability / polite ask | couldn't — past impossibility | |
| Permission | |||
| can | informal permission | can't — refusal of permission | |
| may | formal permission | may not — formal refusal | |
| could | polite request | — | |
| Possibility | |||
| may | real possibility (~50%) | may not — possible non-occurrence | |
| might | weak possibility (~30%) | might not — weak non-occurrence | |
| could | theoretical possibility | — | |
| Obligation & Necessity | |||
| must | strong personal obligation | mustn't — prohibition (NOT no obligation) | |
| have to | external obligation | don't have to — no obligation | |
| need to | necessity | needn't / don't need to — unnecessary | |
| Advice & Recommendation | |||
| should | advice / moral duty | shouldn't — inadvisable | |
| ought to | moral obligation | ought not to | |
| Future & Prediction | |||
| will | prediction / promise / offer | won't — refusal / negative prediction | |
| shall | offer / suggestion (BrE) | — | |
| would | conditional / polite request | wouldn't — conditional negative | |
Advanced Notes
Modal verbs form a system of overlapping meanings — context decides which reading applies. "Could" covers past ability, polite requests, and tentative possibility all at once. Register matters: "may" for permission sounds formal or even stiff in casual speech, where "can" dominates. The must/have-to distinction is real but collapsing in everyday British English — learners often over-apply "must" where a native would say "have to". Modal negatives are false friends: "mustn't" = prohibition, "don't have to" = no obligation — opposite meanings.
FAQ
Must vs have to — what's the difference?
"Must" expresses personal obligation — something the speaker feels is necessary: "I must finish this today." "Have to" expresses obligation imposed from outside — a rule, a law, another person: "I have to finish this by 5 PM, my boss said so." In casual British English the two increasingly overlap, but the distinction is still taught and tested.
Mustn't vs don't have to — do they mean the same thing?
No — they're opposites. "Mustn't" means prohibition (you are not allowed to do it): "You mustn't smoke here." "Don't have to" means there's no obligation (you can choose): "You don't have to smoke if you don't want to."
Can I say "she musts go" or "she must to go"?
No — both are wrong. Modal verbs never take -s, even with he/she/it, and they're never followed by "to": the correct form is simply "she must go."
Can vs could — what's the difference?
"Can" is for present ability, permission, or possibility: "I can swim." "Could" is for past ability, a more polite request, or a more tentative possibility: "I could swim when I was five," "Could you help me?", "It could rain later." Could is not the automatic past of can in every context — for a single past success, "was/were able to" is more accurate than "could".
May vs might — which is more certain?
They're close in meaning, but "may" tends to sound slightly more formal and, in some contexts, slightly more likely than "might," which leans more tentative: "It may rain" vs "It might rain." In everyday speech the difference in certainty is small enough that many native speakers use them interchangeably.
Practice
Word bank — tap a word to fill blank 1
- 1.You wear a seatbelt — it's the law.
- 2. I borrow your pen?
- 3.It rain tomorrow — the forecast isn't sure.
- 4.You see a doctor about that cough.
- 5.She leave early today — her manager said it's fine.
Compare With
Further Reading
Modal Verbs in English: A Practical GuideOther B1 Topics
Present Perfect
Used for past actions that still matter or connect to now
Present Perfect Continuous
Used for ongoing actions that started in the past and still continue
Passive Voice (Basic)
Used for sentences where the action or result matters more than who did it
Used To
Used for past habits or states that no longer exist
Future Continuous
Used for actions in progress at a specific future moment
Question Tags
Used for confirming information or seeking agreement at the end of a statement
Linking Words: However, Although, Despite, In Spite Of
Used for connecting contrasting ideas using concession and contrast markers
Relative Clauses (Defining)
Clauses that identify exactly which person, thing, or place you mean.
So and Such
Use so before adjectives/adverbs and such before nouns to emphasize degree, often followed by a that-clause showing the result.
Order of Adjectives
The fixed order adjectives usually follow before a noun: opinion, size, age, shape, colour, origin, material, purpose.
Future Time Clauses
Use present simple, not will, after when/as soon as/before/after/until/once even when the meaning is future.
Subject and Object Questions
Who broke it? vs Who did you see? — question word as subject or object.
Indirect (Embedded) Questions
Used for asking politely by embedding a question inside a carrier phrase with statement word order
British English vs. American English
Compares the main grammar, vocabulary, and usage differences between British and American English