Is it ok to email my professor something I found related to class? I just stumbled across an article directly related to what we just discussed in class. Is it appropriate to email it to my professor? For some reason it feels improper and I don't want to look like a teacher's pet.
Yes, it's appropriate.  No halfway reasonable instructor would hold this against you.

On the other hand, please don't be disappointed if your instructor doesn't respond contentfully to your email.  Faculty are extremely busy and many get dozens of emails a day, so they have to prioritize which they can respond to.  If you want to have further engagement on this topic, that's what office hours are for.