1. Could
1.1. It used to ask for something, and is the most polite way that can
1.1.1. Syntax
1.1.1.1. affirmative
1.1.1.1.1. He could make a soccer team
1.1.1.2. Negative
1.1.1.2.1. She couldn't drive when she is drunk
1.1.1.3. Question
1.1.1.3.1. Could you hurry to get to work early
2. Can
2.1. Indicates skills or possibilities
2.1.1. Syntax
2.1.1.1. affirmative
2.1.1.1.1. I can study all night
2.1.1.2. Negative
2.1.1.2.1. You can't run 300 miles in 5 minutes
2.1.1.3. Question
2.1.1.3.1. Can you hear me?
3. May
3.1. It used to say that something is possible
3.1.1. Syntax
3.1.1.1. affirmative
3.1.1.1.1. I may be a little late to my house
3.1.1.2. Negative
3.1.1.2.1. You may not go to school in the rain
3.1.1.3. Question
3.1.1.3.1. May you visit your grandparents?
4. Mighty
4.1. It is used to express a possibility but more probability
4.1.1. Syntax
4.1.1.1. affirmative
4.1.1.1.1. This house might fall any time
4.1.1.2. Negative
4.1.1.2.1. The engineer mightn't work because you are sick
5. Have to
5.1. It is used to express that something is very necessary
5.1.1. Syntax
5.1.1.1. affirmative
5.1.1.1.1. I have to travel to EEUU and know it
5.1.1.2. Negative
5.1.1.2.1. She don't has to exceed her capacity credit card
5.1.1.3. Question
5.1.1.3.1. Do you have to play videogame in the morning?
6. Must
6.1. It is used when we think or perform something that is necessary
6.1.1. Syntax
6.1.1.1. affirmative
6.1.1.1.1. I'm hungry, I must cook a food
6.1.1.2. Negative
6.1.1.2.1. You mustn't play drink beer every day
6.1.1.3. Question
6.1.1.3.1. Must I do the homework tomorrow?
7. Ought to
7.1. It means duty, waiting for something to happen
7.1.1. Syntax
7.1.1.1. affirmative
7.1.1.1.1. The Coca-Cola ought to design a new flavor
7.1.1.2. Negative
7.1.1.2.1. Juan oughtn.t train all the time
7.1.1.3. Question
7.1.1.3.1. ought you watch TV for the baseball game?