Modals

Can

1. ability

2. permission

3. theoretical possibililty - Anybody can make mistakes The road can be blocked (It is possible to block the road)

Could

1. past ability

2. present or future permission

3. present possibility (theoretical or factual) - We could go to the concert The road could be blocked

4. possibility or ability in UNREAL conditions - If we had more money, we could buy a car

May

1. permission

2. possibility (factual) - The road may be blocked (It is possible that the road is blocked)

Might

1. permission (rare)

2. possibility (theoretical or factual)

Shall

1. willingness (2nd or 3rd person) - He shall get his money

2. intention (1st person) - We shall overcome

3. insistence - You shall do as I say (I insist on it)

Should

1. obligation

2. logical necessity

3. after certain expressions - It's odd that you should say that I'm sorry that this should have happened

4. in normal real conditions - If you should change your mind, please let us know

Will

1. willingness (in polite requests)

2. intention (usually contracted) - I'll write as soon as I can

3. insistence (no contraction) - We will do it, whatever you say (He insists on it)

4. logical necessity - The game will be over by now.

5. habitual present - Oil will float on water.

6. future

Would

1. willingness

2. insistence - He would do that. (he insists on it)

3. characteristic activity in the past

4. unreal condition - He would smoke too much it I didn't stop him.

5. probability - This would be his mother.

Must

1. oblligation

2. logical necessity