Must and have to are modal verbs in English. This page will guide you to the proper use of these modals.
Must
1. We use must to make a logical deduction based on evidence. It indicates that the speaker is certain about something:
Examples:
- It has rained all day, it must be very wet outside.
- The weather is fantastic in California. It must a lot fun to live there.
2. Must is also used to express a strong obligation.
Examples:
- Students must arrive in class on time.
- You must stop when the traffic lights are red.
- I must go to bed.
Have to
Like must, have to is used to express strong obligation, but when we use have to there is usually a sense of external obligation. Some external circumstance makes the obligation necessary.
Examples:
- I have to send an urgent email.
- I have to take this book back to the library.