Modal Verbs

Modal verbs — can, could, may, might, must, should, will, would — are a special group of verbs used to add meaning on top of an action, rather than just stating it as fact. They let a speaker express things like possibility, necessity, permission, ability, or advice. For example:

She works here

A plain fact

She might work here

A possibility

She should work here

Advice

She must work here

A strong conclusion

Key features

No inflection

Modals do not take -s in the third person singular, past or -ing form.

✅She can swim.

❌She cans swim.

Followed by the bare infinitive

They are always followed by the base form of the main verb (without to).

You must finish on time.

Negation and questions without auxiliaries

Modals form negatives and questions without using "do".

Can you help? (Do you can help? ❌)
You shouldn’t worry.

Modal verbs overview

CAN / COULD / BE ABLE TO

MAY / MIGHT

Must / have to

Will / would

SHALL / SHOULD / OUGHT TO

Perfect Modals

So far, most modals we've covered talk about the present or future — possibility, obligation, advice happening now or later. But modals can also look backward, using the structure modal + have + past participle, to comment on something that already happened. This lets speakers express certainty, criticism, or speculation about the past — not by using past tense forms, but by attaching a modal's meaning (deduction, regret, possibility) to a completed action.

Must have

Can't have / Couldn't have

May have / Might have

Could have

Should have / Ought to have

Would have

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