ما الفرق بين :must/have to ؟

[ابو بيشو]

have to:
We can use 'have to' to express a strong obligation. When we use 'have to' this usually means that some external circumstance makes the obligation necessary.
• I have to arrive at work at 9 sharp. My boss is very strict.
• We have to give him our answer today or lose out on the contract.
• You have to pass your exams or the university will not accept you.
• I have to send a report to Head Office every week.