1. How they are formed
General pattern:
Subject + modal verb + main verb (bare infinitive) Subject + have to + main verb
Examples: must go, should study, may enter, have to work
Rule details
A2 (Pre-Intermediate)
General pattern:
Subject + modal verb + main verb (bare infinitive) Subject + have to + main verb
Examples: must go, should study, may enter, have to work
Must (obligation):
You must wear a seat belt.
Should (advice):
You should drink more water.
Have to (external necessity):
I have to finish this report today.
May (possibility/permission):
You may leave early if you finish your work.
Must vs Have to
Must is often internal/personal obligation; have to is usually external requirement.
Should vs Must
Should is recommendation; must is stronger and mandatory.
May vs Must
May indicates possibility; must indicates necessity or strong certainty (in context).