Modal verbs are helping verbs and they help main verbs to express or to describe a host of situations. Modal verbs are also called auxiliary verbs and they are always used with main verbs as they cannot stand on their own. The use of modal verbs is governed principally by the 9 pure modals - CAN, COULD, MAY, MIGHT, MUST, SHALL, SHOULD, WILL and WOULD. Many situations can be explained or described by the use of modal verbs and it is possible that a modal verb can explain different situations and also a situation can be expressed by different modal verbs.
Specific rules govern the use of modal verbs:
Modal verbs are followed by the base form of a verb – "I MUST COMPLETE my assignment well in time."
A modal can be followed by the base form of the auxiliary verbs BE or HAVE followed by a participle - "Spectators MAY BE WATCHING."
Modals are immune to subject-verb agreements.
Modals don’t use the infinitive form TO except in the case of OUGHT TO.
Questions are formed by interchanging the verb and subject – "I CAN go to the movies" – "CAN I go to the movies?"
The negative is formed by adding NOT after the verb. - "You SHALL NOT go to the movies" or "You MAY NOT sit for the exam'.
Remember that all modals except 'might' and 'may' when used with NOT can be contracted as 'couldn't' or 'shouldn't' or 'can't'. The quiz that follows will test your knowledge of modals.