Must
You must wear a crash helmet on a motorbike - It is the law.
Must not
You mustn't get on a train without a valid ticket.
Have to
You have to stamp your ticket when you get on a bus in Rome.
Cannot
You can't drive a car without a license
Can
You can either take the bus or the metro.
Could
You could take a taxi if you are in a hurry
Should
You should see a dentist if you have a toothache.
Should not
You shouldn't drink alcohol if you are going to drive.
Ought to
Ought not to
You ought not go out in the rain if you don't have an umbrella - It's a bad idea.
Can
I can ride a horse - I had lessons when i was a child.
Cannot
I can't swim - In fact i am terrified of water.
Could
I could speak Danish when i was a child.
Could not
I couldn't drive a car until i had lots of lessons.
Can
Can i open the window? It's too hot in here.
May
May i open the window?
Could
Could you carry this for me? I have too much to carry
Would
Would you get me a newspaper when you go to the shops please?
Will
Will you answer the phone please - I am bus
Shall
Shall i get pizza for dinner tonight?
Shall can only be used in the 1st person I/We - Not he/she/you/It etc..
I shall meet you at the station at 7pm
Might
He might be in the office on tuesday - I'm not sure.
May
She may come to the meeting- she's not sure of her schedule at the moment.
Could
He could be on the fourth floor - he has a meeting there later.
Can't have
He can't have been at work on Tuesday - I saw him at the stadium.
Negative certain deduction
Must have
He must have been in the office - his car was there.
Positive certain deduction
Will
I'll drive you to the station if you want.