I tried to answer this below, but simply could, can and may, might similar depending on tense (past/present) May - May I have some food? - politer - you may eat food Can - Can I help you? - less polite - I can do it. - Can suggests very definite ability Could - I could eat some chocolate - possibility, person is thinking about it Might - I might eat some chocolate - more likely possibility, person is thinking about (and may do it) I believe they are pretty much interchangeable, depending on tense and emphasis.

Hi Miguel THis is a very big subject- usually it takes me an hour or more to teach this subject in a lesson. But briefly- Can- being able to do something (ability) He can speak English but he can't speak French May- permission (question form only I and WE) May I leave the room,teacher? May we play outside, mum? Could- ability in the past "He could see the moon last night". Might- a weak possibility "He might come tomorrow but it's not likely". Should - recommendation "You should study harder if you want to pass the exam". If you book a lesson I can explain it to you better and give you some exercises to help.

Hello Dear Miguel, Can Used to express ability (to be able to do something): I can make jewelry. He can’t speak French. Can you open this jar? Used to ask for permission: Can I use your bathroom? Can I leave now? Can I raise the volume? Used to make requests or suggestions: Can I have more napkins? Can I have the bill? You can take this spot if you like. You can do whatever you want. Could (past form of can) Describes an ability that someone had in the past: I could swim when I was young. You could see the boat sinking. They could tell he was nervous. Often used in auxiliary functions to express permission politely: Could I take this jacket with me? You could borrow my umbrella. Could you please let me pass you? Could I get you more water? Used to express possibility: All of them could ride in the van. You could always stay at our house. Could it be true? This plan could really work out. May Used to ask for formal permission: May I come in? May I say something now? May I ask one question? Used to suggest something that is possible: She may agree with this plan. They may not be happy about what happened. It may shower tonight. Might (past form of may) Used to suggest a smaller possibility than may does (actually, might is more common than may in American English): He might have finished it. I might go see a doctor. I might not come this time. It might be right. You might have lost it. The store might have been closed today. Must Used to express something formally required or necessary: I must complete the project by this week. The government must provide health care for everybody. Everyone must save the natural resources of the earth. The building must have a fire alarm. You must answer my question right now. Used to show that something is very likely: He must be a genius. You must be joking! There must be an accident. She must be very tired.