May, might, can and could

[Rebecca L.]

In the last English exam paper, I lost most of the marks by confusing " may, might, can and could". I don't know how to use them correctly.

Might and could are used in past tense, right?

Among those four, which of them is used in a more polite way?

[Mister Micawber]

Might and could seldom represent the past tense, though they do so sometimes. English has no absolute order of politeness, because more is conveyed in the tone of voice and more depends on relationships than is represented in the words themselves. Nevertheless, a generally acceptable order, from most familiar to most polite, is:

Can I have your purse?
May I have your purse?
Could I have your purse?
Might I have your purse?

All of these are present tense.

Could and might appear in past forms in such as these:

'Can I have your purse?' -- He asked her if he could have her purse.
'May I have your purse?'-- He asked her if he might have her purse.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber