Have to or must?

[Arlindomarco]

Use "must" for strong obligations at the moment of speaking.
Use "have to" for daily responsibilities.
Examples:
I have to catch a train to work every morning.
I must get going.It's late!
Happy New Year!

[Mister Micawber]

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This is not a good 'rule', arlindomarco. HERE is a better explanation.
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_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber

[Alan]

Hi arlindomarco,

Another difference between the two constructions is that 'must' is very often external compulsion and 'have to' is internal compulsion. In other words 'must' is often another person telling you what to do and 'have to' is often you telling yourself what to do. For example:

I must be early for work tomorrow because my boss has told me to be and so I have to get up early.

Alan
_________________
English as a Second Language
You can read my ESL story Here comes 2004...