Hi there! Here’s what I did today to teach the different meanings of the modal verbs:
must / mustn’t
have to / don’t have to
should / shouldn’t
can / can’t
The table is divided in three parts: modal verb (must), meaning (it’s an obligation) and example (We must go to school every week from Monday to Friday.).
Just print the document, cut it out and let your students match the parts. It won’t take them more than 5 minutes. Once it’s corrected, let them find the correspondences in their own language.
Finally, remove everything from the table and take the modal verbs bits. Shuffle them and make your students choose one (without looking) at a time. They should try to remember the meaning of the modal verb and create an example.
It’s much better if you do this right before explaining the grammar, so they can learn actively by discovery and create a long-term knowledge, instead of just being passive learners.