Some TMNT stuff really isn't for little kids.
Metal Head was once a superhero who, along with his friends Battling Bernice, Stainless Steel Steve, Zippy Lad, Doctor Dome, Captain Deadbolt and Joey Lastic founded the Justice Force team. Unlike his friends, Metalhead was not a man but a synthetic being that had been created by Doctor Dome. Finally, the Justice Force separated due to internal tensions simmered over Bernice because of the feelings of Dome and Steve, Steve and his friend Metalhead made it to Northampton and opened a comic book store.
One day, the ex-members of the Justice Force were attacked by Doctor Dome's old Domeoids, because Doctor Dome wanted to draw Bernice out of hiding. Bernice's daughter, Ananda was able, however, to inform dome that Bernice had already died three years earlier, and thus bring him to his senses.
Much later, Casey and April asked Steve and Metalhead to watch their adopted daughter Shadow after Lilith's Sisterhood swears vendetta against her for the death of Sloane. The two super heroes then moved into the Jones Farm, which they have shared with Shadow and Splinter (until his death).
Metalhead is a synthetic dwarfish creature that is able to control his body, especially his hair, psychokinetically. He used it to control his hair, which can also harden to a steely consistency, so that it can serve at will as a living fetter, additional arms or as a stabbing or cutting weapon. For locomotion metalhead's uses his hair by shaping it into spidery legs with which he can also climb vertical walls.
Other effects of its artificial nature, are his ability to change his appearance between his super form and a diminutive man, and his insensitivity to age.