What is the difference between 'might' and 'may'?

[kickassangel]

Having gone to school in the 70s when grammar wasn't taught, i find myself with embarrassing gaps in my knowledge.
however, without jumping all over me, could a more knowledgeable person than myself, tell me a 'rule' for when to use 'may' and when to use 'might'
e.g. please may i ...
i might do that/i may do that.
sometimes i know the right one, sometimes i don't

"The difference between may and might is subtle. They both indicate that something is possible, but something that may happen is more likely than something that might happen. So you may go to a party if Matt Damon invites you, but you might go to a party if your least favorite cousin invites you."

LOL I like this explanation.

There are other differences to.

thank you, so the ones where you HAVE to say 'may' are just convention, really, and my mother picking on me when i was a child?

have just added 'grammar girl' to my favourites!

your mother picking on you could well have been telling you to say "please MAY I" rather than "please CAN I" though? rather than a may/might thing?

no, twas may/might,she still does it. sigh

TinkerBelle's not quite right there ...

may implies that the possibility remains open: "The Mies van der Rohe tower may have changed the face of British architecture forever" (it has been built); might suggests that the possibility remains open no longer: "The Mies tower might have changed the face of architecture forever" (if only they had built it). Similarly, "they may have played tennis, or they may have gone boating" suggests I don't know what they did; "they might have played tennis if the weather had been dry" means they didn't, because it wasn't.

may also has the meaning of "having permission", so be careful: does "Megawatt Corp may bid for TransElectric Inc" mean that it is considering a bid, or that the competition authorities have allowed it to bid?

So you would talk of something that might have been, but of something that may happen in the future?

all fall down, i salute you. that makes sense & is more detailed than grammar girl.