May, might, mustn’t
He may win.
He might win.
He mustn’t win.
When we want to say that something is possible, we use may or might. When we use might, it is less possible. For example, She may be here at six. She might be here at six.
May is very similar to can but there is a little difference.
We use can, when we say that somebody is able to do something.
She can play tennis. – She knows how to play tennis.
We use may, when there is a possibility that somebody does or will do something.
She may play tennis tomorrow. – Maybe she will play tennis tomorrow. It is possible but we are not sure.
When we want to say that somebody is not allowed to do something, we use mustn’t. For example, You mustn’t smoke here.
You can see more examples in the book The Little Prince.