"Must" is most commonly used

to express certainty. It can also be

used to express

necessity or strong

recommendation, although native

speakers prefer the more

flexible form "have to." "Must

not" can be used to prohibit

actions, but this sounds

very severe; speakers prefer to use

softer modal verbs such as

"should not"

or "ought not" to dissuade rather

than prohibit.

+ You must not eat that. IT IS FORBIDDEN,

IT IS NOT ALLOWED.

• You don't have to eat that. YOU CAN IF YOU

- WANT TO, BUT IT IS NOT NECESSARY.

EXAMPLES CAN

• I can speak five languages.

• We can work late tonight if you need us.

• We can work late tonight if you need us.

• Bill and Tom can't help you.

• Bill and Tom can't help you.

• The restaurant can be expensive if you drink a lot of

wine.

• The restaurant can be expensive if you drink a lot of

wine

• It can be dangerous to drive if you are tired.

• It can be dangerous to drive if you are tired.

• Would you mind if I brought a colleague with me?

• Would you pass the salt please?

• Would you mind waiting a moment?

• "Would three o`clock suit you?" - "That’d be fine."

• Would you like to play golf this Friday?

• "Would you prefer tea or coffee?" - "I’d like tea please."

http://www.englishpage.com/conditional/conditionalintro.html

http://www.englishpage.com/modals/could.html