Common helping verbs include "be," "will," "do," "can" and "have." Also called auxiliary verbs, helping verbs modify main verbs to create more complex verb tenses and more nuanced meanings. For example, in the sentence, "the woman can drive a car," the helping verb "can" modifies the meaning of the main verb "drive" from an action to a statement of general ability.
Depending on the method of counting, there are between 13 and 26 helping verbs, with the verbs "be," "have" and "do" considered primary helping verbs. The primary helping verbs can also appear as main verbs. The other helping verbs, including "can," "would" and "must," fall under the category of modal verbs, which cannot appear as main verbs. Modal verbs modify the meaning of the main verb.
The helping verb "be," which includes all its forms including "is" and "am," establishes either a continuous tense or passive voice. Continuous tense indicates an ongoing action, such as "he is fishing in a lake." Passive voice only occurs with the use of a "to be" verb as a helping verb, and allows for sentence construction without an agent for the main verb to act on. For example, the sentence, "the car was driven," does not indicate who drove the car.
The helping verb "have" creates perfect tenses, such as, "she has driven the car."