Modals of Possibility

Modals of possibility show how sure you are about something.

At B1, the most useful forms are may, might, could, must, and can't.

Possible: May, Might, Could

Use may, might, or could when something is possible but not certain.

Meaning	Example
possible now	She might be at home.
possible action now	He may be working late.
possible general fact	That story could be true.

The negative forms are may not and might not.

She might not know the answer.

It may not be open today.

Almost Certain: Must

Use must when you believe something is almost certain because of evidence.

You have been travelling all day. You must be tired.

The restaurant is full. It must be good.

This is not an obligation. It is a strong guess.

Almost Impossible: Can’t

Use can't when you believe something is not possible.

You just ate lunch. You can't be hungry already.

This bill can't be right. It is much too high.

Possibility In The Past

Use may have, might have, could have, must have, and can't have + past participle.

Meaning	Example
possible past	She might have left early.
strong past guess	They must have gone out.
impossible past	He can’t have received the message.

May Be Or Maybe

May be is a modal verb plus be.

It may be true.

Maybe is one word and means perhaps.

Maybe it is true.

Common Mistakes

Avoid	Use
She might knows.	She might know.
It maybe true.	It may be true.
He must to be tired.	He must be tired.
She can not have got it.	She can’t have got it.

Practice

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I am not sure where Liam is. He ___ be in his office.

Summary

Use may, might, and could for possible ideas. Use must for a strong positive guess and can't for a strong negative guess. For past guesses, use modal + have + past participle, as in might have left, must have gone, and can't have known.