"Might" is both the past tense and quasi-subjunctive of "may" and is used when it applies to (a) an event in the past or (b) alternatively a tentative or unlikely situation in the present. Examples: a) "The judge says I may go" becomes in the past "The judge said I might go". b) "I may catch the bus tomorrow" vs. "I might be run over by a bus tomorrow". The main difference between "must" and "have to" is that the latter is not a modal verb, so it can form all the usual verb tenses and compounds, such "I will have to to move when I get my new job", or "I didn't have to move". When you could use both, I think there tends to be a slight tendency to use "must" when it's intrinsically true, versus something that's externally imposed and perhaps could be avoided. I might say "I must go to the dentist, because I have this toothache that won't go away" but "I have to go to the dentist for my teeth-cleaning tomorrow".

Hello, well... The usages of may and might are similar. Although one or the other is more likely to be used in some contexts, neither choice will be wrong. Below is an introduction to the most important uses of may and might. 1. May and might are both commonly used to talk about possibility: You may have a little difficulty driving at night. I might have an allergy to wheat. We may go to London for vacation, if we can still afford it. Note that many grammar books say it is better to use might when something is less likely, and may when something is more likely, but this is a flexible rule.