Board Thread:Questions and Answers/@comment-28617495-20160601073159/@comment-24835246-20160605122424

Techincally, since Happstablook (Mettaton's ghost form) is proven to be of ambiguous gender in-game, Mettaton has no gender. His robot body was made to be a male, but that doesn't mean that Mettaton actually is a male. So in some senses, Mettatonis a male, and in others, he has no gender at all.