Difference in grammar between must and have to

Question

Could someone please explain the difference between Must and have to??? it is so complicated to understand the difference... Should i use "must" for obligations and "have to" to give pieces of advice?

Answer 1

Both "must" and "have to" can have the same meaning of requirement or obligation

You must finish your vegetables before you can have dessert.
You have to finish your vegetables before you can have desert.

You must water the plants or else they will die.
You have to water the plants or else they will die.

though "must" is usually considered to be an intensifier and stronger.
A lot depends on context.

However, the negations have different meanings

You must not open the door.

implies a requirement which needs to be fulfilled.

You don't have to open the door.

implies a request which may or may not be fulfilled.