Final answer:
In the sentence provided, "can" is a helping verb that is part of the verb phrase "can come," where "come" is the main verb that indicates the action of the sentence.
Step-by-step explanation:
The highlighted word "can" in the sentence "We can come over for lunch today." acts as a helping verb. In this case, "can" is used to express ability or permission, supporting the main verb "come", which indicates the action of coming over.
Together, "can come" form a verb phrase with "can" being the auxiliary or helping verb and "come" being the main verb. Helping verbs are used alongside a main verb to enhance or change the meaning slightly, but on their own, they do not indicate the action of the sentence.