To express ability/capacity in the past, for example – He could walk very fast in his youth.To express ability or capacity, for example – I can run very fast.To express permission, for example – You can go home now.They express meanings or ideas such as permission, possibility, certainty, necessity, obligation, command, compulsion, ability, capacity, etc.Ĭan, could, may, might, shall, should, wall, would, must, ought to, need to, have to, used to, dare, etc.Ĭouldn’t, shouldn’t, mustn’t, needn’t, wouldn’t, ought not to, etc. They are always used with the principal verb that follows them. Modals definition for kids: The words that describe the mode or manner of the action denoted by the verb are called modals.