Question

When something is mottled, it can be attractive like a butterfly’s wings and a dog’s fur.

Answer 1

Yes, you should put a comma.

A comma is usually used in the middle of a sentence to separate two clauses, or right before a conjunction. Since “like” is a dependent clause in this sentence, as “it can be attractive” can stand alone, a comma would be put before it. It may also help to read the sentence and see if there is a natural pause to it.