Lexical verb is the main verb which can stand alone in a sentence. Lexical verbs are an open class type of verb and are used to express states and actions. Needless to say it is very important in forming the sentence.
It is not sufficient to express all the meanings. For example, ideas like questioning, negation, time, repetition, completion, willingness, obligation etc cannot be expressed by using the simple forms of the verb. In order to express these ideas, a number of helping or Auxiliary verbs are used.
Primary auxiliary verbs-
Be: is, are, am, were, was, being, been.
Do: does, did.
Have: had, has
Usage of these auxiliaried can be categorized like this,
- Making the sentence complete and meaningful. eg. It is an honor for me to be standing here with you.('be'- helping verb)
- In negative sentences and questioning. eg. I do not want to cry./Do you want something?
- Helping in the formation of passive voice. eg. Flowers are plucked by the girls.
- Expressing continuous tense of the sentence eg. He is reading a book.
So these auxiliaries are substancial in the usage og language.