Using May and Might

Two other important modal verbs are may and might. The two are used interchangeably in standard American English to express probability or possibility:

--You may be wrong.
--You might be wrong.
--The attorney might be late.
--The attorney may be late.

The past form is expressed as follows:

modal (may/might) + have + past participle

--I may/might have left my glasses in the restaurant.

NOTE: Must can also be used to express probability:

--The plane must be leaving now.