Range of modals
- Ability/permission: can, could, may.
- Obligation: must, have to, need to.
- Advice: should, ought to.
- Deduction: must (certain), can't (impossible), might (possible).
Common errors
- Wrong: must to go. Right: must go.
- Wrong: can able to. Right: can / is able to.
Key idea
Modals express ability, obligation, advice and deduction; they are followed directly by a base verb with no 'to'.
Remember
Never write 'must to' or 'can to' — a modal is followed by the base verb.