slug: modals title: Modal Verbs group: structures order: 3 summary: Express ability, permission, obligation, or possibility using a modal auxiliary before the base verb. formula: S + modal + V(bare)
When to use it
Modal verbs modify the main verb to express a speaker's attitude toward the action — whether something is possible, necessary, allowed, or advisable. They are never inflected: no -s in the third person, no -ed for past, no -ing.
You should study every day if you want to improve.
Each modal carries a distinct meaning. The same modal can have more than one meaning depending on context.
Form
| Modal | Primary meaning | Example |
|---|---|---|
can | Ability / permission (informal) | She can speak three languages. |
could | Past ability / polite request / possibility | He could not find his keys. |
may | Permission (formal) / possibility | You may leave early today. |
might | Weak possibility | It might rain later. |
must | Strong obligation / logical certainty | You must wear a helmet. |
should | Advice / expectation | You should eat more vegetables. |
will | Future intention / prediction | I will call you tomorrow. |
would | Polite request / hypothetical | Would you help me? |
To form the negative, add not directly after the modal: cannot, could not, should not. Contractions (can't, couldn't, shouldn't) are common in speech and informal writing.
Examples
- You must not park here — it's a fire lane.
- Could you pass the salt, please?
- She might not come to the meeting; check with her first.
Common mistakes
- Adding
-sfor third person: "She cans swim" → She can swim. - Using
toafter a modal: "You must to study" → You must study. - Confusing
must(obligation from the speaker) withhave to(obligation from outside rules) — they differ in negative meaning: "You mustn't go" (forbidden) vs "You don't have to go" (not necessary).