Metal Sonic is the robotic creation of Sonic the Hedgehog created by Dr. Eggman and is a minor character in Super Smash Bros. Brawl Crossover. His first appearance is in Brute Brawl where he is seen fighting The Covenant alongside Knuckles the Echidna and Shadow The Hedgehog and is instantly destroyed when the Brutes splatter him with their Gravity Hammer. He is later repaired by their chieftain Tartarus and is used by the Brutes to help them locate the Metalers.
Metal Sonic was created by Dr. Eggman to max the skills of Sonic the Hedgehog and fight him, over years he has become his rival and fought him on Green Hill Zone to search for the Chaos Emeralds for Eggman. Years later he travels to Earth in the region of Scandinavia during a blizzard to explore how the environment of Earth is like, Metal Sonic sees The Covenant fighting with the ODST whom are being led by Master Chief, Shadow The Hedgehog, Knuckles the Echidna, and Solid Snake, wondering who to join due that they are both threats of him, he is then attacked by Brutes who are armed Brute Plasma Rifles, as he hides in the rocks, he attempts to retreat only to be snatched by Master Chief and Solid Snake who is beaten up by Master Chief having Solid Snake(who has a intense dislike to hedgehogs) severely damaging him by smashing him side by side and throw him towards Knuckles and Shadow being cornered by him. Suddenly he along with Shadow and Knuckles encounter a Brute Captain Major who is armed with a Gravity Hammer and as Metal Sonic tries to fight the Brute, his attacks do not seem to inflict damage on the Brute only to anger the Brute. Metal Sonic is then crushed and flattened by a frenzied Brute instantly destroying him, Shadow witnesses and soon discovers that the power of a Brute's Gravity Hammer is deadly enough to kill a hedgehog. Metal Sonic is later reconstructed by one of the chieftains Tartarus is now used as his slave. Tartarus begins interrogating him about asking what he knows about an ancient undead shape shifting species capable of infecting others especially robots. Later during the episode of Death Battle Underground he is seen fighting other combatants alongside Metal Knuckles, the Brutes, and Imperator Ix. Metal Knuckles suddenly discovers that the lieutenant of the Metalers, Medusa has spread and occupied several bases across the universe that she is now even capable of fighting and participating in Death Battles resulting in Tikal the Echidna becoming angered, jealous, and annoyed of her high ranks and popularity. Metal Knuckles becomes shocked and frightened, and fears that he, his best friend Spartan Joaquin, and the rest combatants can be infected by her, Metal Sonic is pushed by Metal Knuckles into the arena to take on Medusa. Metal Sonic cornered up by the ruthless and vicious Metaler, begins to cower and has no ideas of how to defeat her(since she can infect him if he tries to touch her). He begins planning an idea to escape beginning to run fast and then attempts to knock down the door with his feet, somehow he is unable to break the doors due that the doors are heavily armored and damages his feet. Metal Sonic begins using his attacks on her but Medusa dodges all his attacks. Medusa begins using her new Metalers weapons on Metal Sonic and damages him. Due to the fact that he is a robot and not an animal, Metal Sonic gets his arm infected from the blasts shot by her and tries to get it off only to have his other arm attached with Metalers and is snatched and completely infected by her becoming a Metaler. Now a Metaler, Metal Sonic becomes a new form known as Metalhog(Play on Metal and Hedgehog) goes out of control behaving like a wild bear and fights off Imperator Ix, however due to his species being an animal he is unable to become infected and defeats Metalhog. Metalhog is soon run over by a modified SVU driven by Metal Knuckles killing the Metal infected robot
While Metal Sonic usually behaves aggressive, violent, and cold-blooded. He behaves more cowardly when he encounters more powerful foes such as the Metalers, Solid Snake, The Covenant, Spartans, Joaquin Douglas, and the Brutes he behaves more pessimistic and weaker than Metal Knuckles being severely damaged by any human, alien, or Metaler