May is a modal auxiliary verb. There is no –s in the third person singular.
- She may be here soon. (NOT She mays …)
May is followed by an infinitive without to.
- You may be right. (NOT You may to be right.)
- He may come.
Questions and negatives are made without do.
- May I come in, please? (NOT Do I may come …)
- He may not come. (NOT He do not may come.)
May is used to talk about possibility, and to ask for and give permission.
- It may rain this afternoon.
- May I play carroms, mummy?
- Yes, you may.
May is used to talk about the chances of something happening.
- I think it is going to rain. You may be right.
- There may be a strike next week.
- Where is John? He may be out shopping.
May well is used to suggest a strong possibility.
- I think it is going to rain. You may well be right.
May is not normally used in direct questions about probability.
- Are they likely to help us? (BUT NOT May they help us?)
But note that may is possible in indirect questions about probability.
- May we not be making a big mistake?
May + perfect infinitive
The structure may + perfect Infinitive (have + past participle) can be used to say that it is possible that something happened or was true in the past.
- Alice is very late. She may have missed her train. (= It is possible that she missed her train.)
May + perfect infinitive can also refer to the present or future.
- I will try phoning him, but he may have gone out by now.
- May I come in?
May is used to give permission; may not is used to refuse permission and to forbid.
- May I come in? Yes, you may.
- May I have a look at your papers? No, I am afraid you may not.
Must not is also used to forbid. It is stronger than may not.
- Students must not use the staff car park.
May and might are not normally used to talk about permission which has already been given or refused, about freedom which people already have, or about rules and laws. Instead, we use can, could or be allowed.
- Can you/Are you allowed to park on both sides of the road here? (More natural than May you allowed …)
- When we were children, we could watch TV whenever we wanted to. (NOT …we might watch TV …)
May in wishes and hopes
May is used in formal expressions of wishes and hopes. May often comes at the beginning of the sentence.
- May God bless you!
- May you both be very happy!
- May the devil take him!
- May you prosper in all that you do!