May expresses likelihood while might expresses a stronger sense of doubt or a contrary-to-fact hypothetical. The difference in degree between “You may be right” and “You might be right” is slight but not insignificant: if I say you may be right about something, there is a higher degree of probability that you are right about it than if I say you might be right about something. Example: You think Einstein is the most brilliant physicist who ever lived? You may be right. / You think it’s going to rain this afternoon even though the sun is shining this morning? Well, you might be right. May expresses likelihood while might expresses a stronger sense of doubt or a contrary-to-fact hypothetical: We might have been able to go if Keir had not been so slow to get ready.