we use have to when we are dealing with strong obligation as same as rules ,you have to stop at traffic light , you have to cure your disease it is really dangerous , must talks for special obligation where every body used for his principal ,obligation I must care about my father,you must spick correctly

It's too late, I must go. or I have to go. - no differents but I must present a passport in the airport. and I have to go home early today, cause i will go to work tomorrow "Have to" has similar meaning with "must" As my teacher told me "must" much stronger verb than the verb ''have to' )

We use "must" to show that is certain something is true. We use "have to" to express a strong obligation, it usually means that some personal circumstance makes the obligation necessary. Examples: - You must be worried, that she is coming home late. - I have to arrive at my work on time.