Believes
A turtle will need attention / A turtle would need attention.
Offers
Can I help you? / May I help you
Probability
May she want pasta? / Could she want pasta?
Obligation
Must I go to school?
Ability
Can he drive a car? / Could he drive?
Believes
Would she want pasta? / Will she want pasta?
Permission
Can it stay? / Could it stay?
Offers
Can / Could / May I pay that bill?
Suggestions (Soft)
You could pack now
Prohibition
Mustn't I eat that food?
Request
Can / Could you buy fast food?
Deduction
They must be on the bus / They may be on the bus? / They could be on the bus.
Suggestions (strong)
You should pack now.
Request
Will you pay this bill? / Could you pay this bill? / Would you pay this bill?
Probability
May / Can he drive now?
Prohibition
You mustn't pay for that.