1. Modals take any subject before them. There is no Subject-Verb agreement problem
2. No two modals co-occur in a sentence.
Eg. The film will be released next week
3. The main verb will always be the V1 form after the modals.
Eg. He cannot move the big stone
4. Past form of some modals stands for 'politeness'.
Eg. i) Would you like to have some tea?
ii) Could you lend me your book?
a) He can sing for eight hours at a stretch.
b) You could take an umbrella, it's raining outside
c) We should complete the shooting by tomorrow evening
d) Shall I wait till you come?
e) The time was up but the makeup person would not turn up.
f) The car hasn't arrived yet. It must've got a flat tyre.
g) There may be heavy rains tomorrow. So, why couldn't we go for indoor shooting?
h) Will you join us for tea?
i) The agreement between the two parties shall be in force for two years.
j) It might be an idea to postpone the release of the film.