Not everything is 100% guaranteed to happen in life. This is why we need the verbs may, might, and could, which are verbs that tell the listener how possible or certain something is, when we talk about events or situations that are possible in the present or future.

Examples

Let’s say: you want to go on vacation, but you are so busy at work that you’re not sure if you can go. Your friend then asks you about your vacation plans. You could answer in several ways:

“I may go on vacation; I’m just not sure if I will have time.”
“I might go, but I’m too busy to commit.”
“I could go if I wasn’t so busy!”

May, might, and could have very subtle differences in the amount of possibility they represent.

May = a possibility (~50%)
Might = a smaller possibility (~30%)
Could = a possibility, a choice

Note: “Could” can mean the past of can, but here, “could” refers to being possible in the present or future.