[Mettaton shakes his head, perhaps in a slightly overexaggerated manner that sets his hair askew. He laughs, brushing his bangs back over his busted eye and the exposed circuitry around it before speaking again.]

No, no!! I'm not a human at all!! I never was!!! But you know, I can understand how that is something humans aspire to create!! I am pretty great!

...Hmm. What made me want to be a robot? It's simple!! Ghosts like me always aspire to possess a body and become corporeal!! I just didn't want to follow in my family's footsteps and possess a training dummy! I mean...gross, right?! So I had a friend help me out and make me a body I liked!!