May is used to express permission. May not is used to deny permission.
- May I come in, sir?
- Yes, you may.
- May I go home now?
- No, you may not.
Now-a-days to deny permission we often use cannot instead of may not. This usage is probably encouraged by the fact that the contraction can’t is easier to say than the contraction mayn’t.
May is also used to express possibility.
- It may rain.
- She may come.
- He may get good marks.
May is also used in expressing a wish.
- May God bless you!
- May his soul rest in peace!
May is used in subordinate clauses that express a purpose.
- Farmers use fertilizers so that they may have a rich harvest.
- We eat that we may live.
Might is the past tense of may in indirect speech.
- He said, ‘I may stand for election.’
- He said that he might stand for election.
- Alice said, ‘I may come.’
- Alice said that she might come.
Might and may
Might shows less possibility than may.
- It may rain. (Maybe a 50% possibility)
- It might rain. (Maybe a 30% possibility)
May and might are followed by an infinitive without to.
- He may come. (NOT He may to come.)
- I might pass. (NOT I might to pass.)
Questions and negatives are made without do.
- May I go? (NOT Do I may go?)
There is no -s in the third person singular.
- She may pass. (NOT She may passes.)