1.ability: Boris can speak three languages fluently. 

2.permission: you can have a break any time.

3.Theoretical possibility: every person can take his right.

can

1.past ability: Tom couldn’t climb the tree.

2.present or future permission: can I drive your bike.

3.present possibility: they could participate in the celebration.

4. contingent possibility: if she had enough time, she could help her niece. 

could

1. permission: you may take a leave if you are in need.

2. possibility: the water may be cut.

may

1. permission: might my brother come with me ?

2. possibility: the boss might give promotion to the staff.

might

1.willingness: the team shall win the game

2.intention: workers shall get their rights.

3.insistence: officers shall be obeyed.

shall

1.obligation: drivers should respect traffic rules.

2.putative use: we are displeased that this problem should have taken place.

3.contingent use in the main clause: he should like to get the job if he was qualified.

4. in formal real conditions: please inform us earlier if you should admit the hospital.

should

1.willingness: will you have a piece of cake ?

2. intention: they will not take more than their need.

3. insistence: the coach will keep advising to get better results.

4.prediction: a. specific: the certificates will declared by now.

                        b. timeless: smoke will raise from the chimney.

                        c. habitual: she will continue lending money if nobody warns her.

will

1. willingness: would you mind helping them?

2. insistence: this is absolutely wrong that you would come close to the fire.

3. characteristic activity in the past: Sally would make a mess of that situation.

4. contingent use in the clause: your brother would disrespect others if you didn’t control him.

5. probability: this wouldn’t be the right address. 

Would

1.obligation in the present: students must work hard before the exam.

2. logical necessity: that must be the right signal.

must

Obligation: logical necessity: they ought to finish early.

                      Expectation: you ought to be the new student.

Ought to