may, might, may have and might have

We make questions by putting the subject after may/might:
May I …? Could I … Might I …? Etc.

The negative forms are may not and might not..

We use may:

• when we are not sure about something:

Jack may be coming to see us tomorrow.
Oh dear! It’s half past ten. We may be late for the meeting.
There may not be very many people there.

• to make polite requests:

May I borrow the car tomorrow?
May we come a bit later?

When we use may not for a refusal it is emphatic:

You may not!
You may not borrow the car until you can be more careful with it.

We use might:

• when we are not sure about something:

I might see you tomorrow.
It looks nice, but it might be very expensive.
It’s quite bright. It might not rain today.

• As the past tense of may for requests:

He asked if he might borrow the car.
They wanted to know if they might come later.

• For very polite requests:

Might I ask you a question?
Might we just interrupt for a moment?

We use may have and might have to show that something has possibly happened now or happened at some time in the past:

It’s ten o’clock. They might have arrived now.[= Perhaps they have arrived]
They may have arrived hours ago. [= Perhaps they arrived hours ago.]