Helping verbs always help either an action verb or a linking verb.
I will play the piano. (will = helping verb, play = action verb)
I will be a teacher. (will = helping verb, be = linking verb)
Some verbs can function as main verbs or helping verbs, but they will only do one job at a time in a sentence.
I have a cat. (have = main verb, action verb)
I have been reading a great book. (have = helping verb)
I am a teacher. (am = main verb, linking verb)
I am cooking dinner for my family. (am = helping verb)