Is like an adverb?

Yes, the word like can be an adverb, a verb, a noun, an adjective, conjunction, or a preposition. Example sentences:

As an adverb: You may not believe it but she's more like forty than twenty five.

As a verb: I like this movie, you will like it also.

As a noun: They had a very elaborate wedding, the like of which you only see in the movies.

As an adjective: They sell towels, bedding, drapery, and like household goods.

As a conjunction: They seemed fine like everything was alright.

As a preposition: She slept like an angel.

And, some people use like as an interjection, but it can be annoying: It was, like, really great!