'May' and 'might'

When faced with the choice, you should primarily consider the degree of probability you wish to express.

'May' is used to express a very high degree of probability (bordering on certainty) that something will happen:

• I may be tired Monday morning.

Furthermore, 'may' is also used to request or grant permission:

• May I call it a day?
• Yes, you may.

'Might' is typically not used in the context of permission. Instead, 'might' is used when you want to express a weaker degree of probability or a more uncertain outcome:

• I might be back later.

'Might' is also used to describe hypothetical situations:

• If I went to bed earlier, I might feel better."