Metalhead is a rogue robot turtle that first appeared in the 1987 cartoon series. Krang imbued Metalhead with the thoughts and memories of all the turtles in episode "The Making of Metalhead".
Teenage Mutant Ninja Turtles (1987 series)
Because Metalhead had all the turtles personalities, it was subject to dissociative identity disorder. Donatello later reprograms Metalhead to fight for the turtles, but because of its instability due to the multiple personalities, Metalhead went haywire and attacked everyone, Donatello was able rig some of the broadcasting equipment at the Channel Six News Building to deactivate Metalhead. Metalhead realized that the Turtles were his friends and became their servant. He was only seen again when Donatello tries to get him to vacuum their TV room in episode "Big Bug Blunder".
His original action figure bio described him as "The original Party robot!". The figure featured an arm with swappable mecha-nunchuks, a backpack with scanner and video games, and vac-metallized detailing. The figure was later re-issued as a roboticized Michelangelo.
Created in the lab by Dr. Harold Lillja, and was discovered by Angel while she was rambling through his things. The robot was still in need of some fine tuning, and during a test run it malfunctioned and began attacking Angel, Harold, and Donatello. After a quick battle, Metal Head was defeated by Angel after donning an experimental exo-suit created by Harold.
Assault on Technodrome
Believing Krang to be the greater threat in regards to the world's safety. Donatello embarks on a solo mission to defeat Krang and destroy the Technodrome. His first part of his mission is to get Metal Head functional again. Donatello believes that an alliance with the Shredder will help accomplish this goal; using Metal Head to meet Shredder, he tells him his plan on how to defeat Krang. Shredder obliges to help him but warns that he will kill Donatello at the first sign of treachery; with this said, he leaves Rocksteady and Bebop to watch Donatello and await his orders.
During the battle, Krang gains the upper hand and reveals to a bloody Shredder that he was in fact betrayed. Shredder honors his word to have his two henchmen kill Donatello, and during the attack Metal Head whom is now controlled by Harold fights valiantly but is nearly destroyed by Rocksteady. From there, Rocksteady and Bebop double team, pummel, and nearly kill Donatello smashing his shell with a sledgehammer.
Splinter and the Turtles recover Donatello whom was severely beaten by Rocksteady and Bebop and even thought to be dead. The Fugitoid, Honeycutt, returns from Dimension X with good news but learns what has happened to Donatello. He senses a pulse then realizes there's time to save the turtle. He uses some of his own tech, and together with Harold is able to bond the turtle's mind with Metal Head, while the turtle's body can be taken care of. He's next referred to by Michelangelo as "Robo-Bro". As Metal Head, Donatello gets his first taste of battle by driving off Koya and Bludgeon; next he engages Baxter Stockman's army of Flyborgs utilizing its power.
Later on after a meeting with Karai and the Foot Soldiers; Splinter issues a challenge against the Shredder pitting his turtles against Shredder's own mutants in "The Gauntlet". The Turtles with Metal-Head/Donatello engage Koya, Bludgeon, Bebop, and Rocksteady. Individually, the turtles do horribly against the brutes with Koya getting the best of Metal Head.
Soon, the brothers begin to work towards their strengths with Metal Head doing quite well eventually blinding and defeating Bludgeon. Soon Bebop and Rocksteady whom were fighting Raphael and Michelangelo are all that is left. Metal Head devises a plan and then self-destructs heavily weakening the two brutes leaving behind nothing save for fiery scrap. Donatello then appears landing the final blows defeating the Foot's last two strongmen.
Powers and Abilities
Metal Head possesses superhuman strength being able to punch holes into the ground. Along with his ability to morph into a four wheeled vehicle; he possesses various weapons such as a laser beam fired from his eyes, anti-gravity gauntlets, machine guns, a flamethrower, and a strong self-destruct sequence.
The robot isn't very durable due to Angel stopping it with an anti-gravity attack of her own, plus Rocksteady was able to easily over-power him.
Metal Head makes an appearance in the second stage titled "Alleycat Blues" as an end stage boss. He battles with a laser gun weapon from his chest along with limb extension punches and kicks.