Mettaton tilts his head to the side, nodding a little as if he's really digesting their words. He hums a bit, no longer swinging the mirror back and forth. He holds them very still and stares at them for another moment before speaking.

"Fascinating, really. Even when you are in a position of utter helplessness your disgusting nature still shines through to make you completely worthless to any and all aid."

He throws them up a little in the air, reaching out to catch one of their legs and dangle them upside down. He's a little disappointed that he succeeded in catching them at all but c'est la vie.

"If you were ever truly in danger would you be able to accept help? I doubt it."

It's not like he's actually offering any real help whatsoever so his words are way more empty musing than any genuine worry for the human.