This document discusses the use of modal verbs to express levels of recommendation. "Should" is used for advice and things that are a good idea. "Have to" expresses strong recommendations for things that are necessary or important. "Must" conveys strong obligation and is often used for rules, with "must not" indicating something is prohibited.
2. Should
Use should to talk about recommendations. It is often used for
things that you think are a good idea (advice).
You should come to work on time.
You shouldnt go to bed so late.
Should he accept that job?
4. Have to
Use have to to talk about strong recommendations,
things that are necessary or important.
You have to come to work on time.
Dont/doesnt have to means it is not necessary, but you
can do it if you want:
You dont have to work after 6.
6. Must
Use must to talk about strong recommendation, things that are
important or are a personal obligation; also rules are often
written using must:
-I must stop drinking alcohol
-All applicants must provide valid documents.
Must not means it is not allowed:
You must not smoke cigarettes on the common areas.