Should similes, when it comes to grammar, be treated/considered as subordinating conjunctions of comparison (e.g. just as, though, etc.)? And therefore, they shouldn't be preceded by a comma (unlike coordinating conjunctions when they introduce an independent clause)?
They played energetically like a pup.
He worked on the math problem until night like an obsessed person.
She goes to sleep after the sun goes down as if she were a nocturnal animal.
Or maybe similes should be preceded by a comma when there's an adverb or adverbial clause in front of them?