Difference between may and might

One of my tutees asked me, "Teacher Serena, what is the difference between 'may' and 'might'?" Do you know the difference?

Both the words are auxiliary verbs. They are used to either express possibility or seek / give permission.

Examples of usage:

(1) I may be able to attend the party tonight. (express possibility)

(2) You may leave the hall now. (give permission)

(3) May I go to the toilet? (seek permission)

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(A) "May" expresses a possibility that is stronger than that expressed by "might".

A.1 I may attend the party tonight. (express a possibility)

A.2 I might attend the party tonight. (express a lower possibility)

(B) As "may" expresses a higher possibility, it will be used in expressions of good wishes instead of "might". If we use "might", we will appear insincere.

B.1 May you have a good trip. (Correct)

B.2 Might you have a good trip. (Incorrect)

(C) When we change a sentence from direct speech to indirect speech, if the reporting verb is in the past tense, "might" is used in the indirect speech in place of "may" because of backshifting.

Example:

C.1 Direct Speech: Mrs Tay said, "The match may be postponed."

Indirect Speech: Mrs Tay said that the match might be postponed.

(D) Use "may" in concessions.

D.1 I may not be pretty but I am kind-hearted.

~ Serena's Greenhouse