While ordinary verbs denote an action or a state, modal verbs express somebody's attitude to an action or a state from the point of view of its necessity, possibility or desirability.
Modal verbs have no groups of tenses, - most of them have two tenses (present and past) or even one tense.
Most of them do not take an auxiliary verb to do to form their negative and interrogative forms.
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Some of modal verbs are followed by the bare infinitive, others by the to-infinitive.
There are the following modal verbs in English: