What are some examples of helping verbs?

Examples of helping verbs include "to have," "to do" or "to be." Also known as auxiliary verbs, helping verbs do not perform the primary action of a given sentence, but they help the primary verb.

Without helping verbs, many sentences do not make any sense. For example, in the sentence "She is writing a long essay," the third person present tense form of the verb "to be" (is) must precede the primary verb (writing). Modal helping verbs such as "can/could," "may/might" and "shall/should" must be added to primary verbs if the speaker wishes to indicate change (e.g. "You should not skip school.")