I agree with most of this, but I think you can use 'might' to ask for permission. Granted, I do realize many people do not use it in that way, but I've heard and also use it from time to time.sperdomo said:Hola
May and might can be used for prediction, permission, advice, or logical probability.
Only may is commonly used in American English to ask permission.
May I go to the store?
May I sit down?
Can I sit down? -----much less formal
Might I sit down? ---This can be found in books, but is rare in conversation, at least in my dialect of American English.
It will rain --- strongest prediction
It may rain --- less sure
It might/could rain. ---slightly less sure (although native speakers will probably argue about which is weaker, may, might, or could)
Someone's knocking at the door..
It must be Mary ---strong possibility
It should be Mary-- less strong
It may be Mary --less strong
It might/could be Mary --weakest
Might can be used to give polite advice but not may
You must revise this ---strong and demanding
You should revise this ---less strong
You might revise this ---very weak advice
You may marry him -- doesn't imply advice...gives permission
To make things more complicated, there are some shifts in meaning in the negative and not all of these forms can be made into questions, for example, Might you revise this? or May it be Mary? Both are awkward. Let me know if you want all of those rules too. I assume you don't! Good luck!