Modal verbs of Probability – must, might, may and could

Impossible (0%)	Possible (50%)	Only possibility (100%)
can’t	might may could	must

We use modal verbs of probability when we have thought about something and we say the possibility of something happening. We don’t know for a fact but, having thought about it we can say what we believe.

Might, could and may all have the same meaning, namely that’s it’s possible. We use might and could more in conversation while may is more formal.

Examples

It’s midnight. John can’t be at school. He mustbe at home. He mightbe asleep.
I don’t know her very well. She mighthave a sister.
He was exhausted. He mustbe sleeping.

Present

I don’t know her very well. She might have a sister.
It’s a great film. You should go and see it.
You ought to call her. She’s worried.

Past

She hates rap music. She can’t have gone to the concert.
They might have told me. I don’t remember.
The car isn’t in the garage. John must have taken it.

Now

He could be working, I’m not sure what hours he’s working this week.
It’s midday. She can’t be sleeping.
There’s a lot of noise coming from that house. They must be having a party.