Metal Sonic (IDW)

"Lord Eggman repaired me. Removed the rebelliousness from my coding. But you know this—we've clashed since then. He decided to upgrade me to this form again. I was to be his greatest weapon in the final battle. But I was completed too late. The war was lost. You had ruined everything once again. I was given the doctor's bio-data. His genius. His drive. His vision. But I serve the Eggman Empire. The only one who can truly rule it is Dr. Eggman. I decided I would use his persona to ensure his rule remained unbroken. I will conquer the world for Eggman as Eggman. And you will tell me where he is so I may hand over control to him."

- Metal Sonic to Sonic the Hedgehog.

Metal Sonic, better known as Neo Metal Sonic, is the main antagonist of the IDW Sonic the Hedgehog comics. He is Sonic's robotic copy and rival, and the current leader of the Eggman Empire.

Past
Much like his videogame counterpart, Metal Sonic upgraded himself to the more powerful form of Neo Metal Sonic, rebelled against his creator Dr. Eggman and took control of the Eggman Empire, plotting to copy the bio-data of Sonic and his friends as to empower himself and take over the world. However, his plot was eventually discovered, and he was defeated by the combined efforts of Team Sonic. Following this, Eggman removed Metal Sonic's rebellious streak to make him more obedient, and he would then clash with Sonic several more times.

During the war between the Eggman Empire and the Resistance, Eggman decided to upgrade Metal Sonic to Neo Metal Sonic once more as a last resort, using a phantom of Metal Sonic created by Infinite to fight while he was being upgraded. Metal Sonic's upgrade also gave him Eggman's bio-data, granting him the former's genius, vision and drive. Unfortunately, by the time Metal Sonic's upgrade had finished, the war had been lost to the Resistance and Eggman had disappeared.

With Eggman gone, Metal Sonic became the new leader of the Empire, yet, due to his programming, still believed that Eggman was the only one who could lead it. Thus, Metal Sonic assumed Eggman's identity using his shapeshifting to ensure his reign remained unbroken, planning to find and hand the doctor's identity back to him once he had successfully conquered the world.

Aftermath
One month after the war, Metal Sonic, still disguised as Eggman, made his first move by taking control of the wayward hordes of Badniks scattered across the planet, and directing them into more organized attacks on various villages. He then held a "trial" for Sonic (whom he kept a close eye on via a Flapper) by ordering a Badnik battalion to attack a village. Sonic, with help from Tails, emerged victorious, and so Metal Sonic decided to organize another attack to ambush him, also making sure to lure in core Resistance member Amy Rose so that they could both be destroyed. This plan also failed, however, and Metal Sonic, much to his annoyance, noticed that Sonic was deviating from his predicted path. Upon being informed of where Sonic was headed next by Orbot, Meta Sonic hoped that Rough and Tumble could finish him off.

Although the skunk brothers failed, Metal Sonic learned from surveillance footage that Knuckles was not guarding the Master Emerald on Angel Island, which meant his plans could accelerate significantly. While surveying his forces via Flapper, Metal Sonic caught sight of Sonic and the Chaotix before the Flapper was destroyed by Charmy Bee, making him suspect that his forces either found a new settlement or that Sonic had figured him out. Following Sonic and the Chaotix's encounter with Shadow the Hedgehog and Rouge the Bat, Orbot informs Metal Sonic that the Egg Fleet is getting into position, prompting him to join up with it to carry out the next phase of his plan.

Identity Revealed
When Sonic infiltrates the Egg Fleet to get information on Eggman's forces, he comes face to face with Metal Sonic, still using Eggman's identity. However, Sonic immediately dismisses the "faker" being the real Eggman, having met with him before and knowing he still has amnesia, causing Metal Sonic to reveal himself and demand that Sonic tell him where the real Eggman is. Sonic then begins to fight with Metal Sonic, but the latter gets the upper hand by copying his bio-data. Figuring he is outmatched, Sonic decides to escape, and Metal Sonic sends his forces to stop him.

Grabbing Sonic by the chest, Metal Sonic demands that he tell him where Eggman is, although he makes him break his grip and falls. Believing that Sonic has fallen to his death, Metal Sonic proclaims himself as the one true Sonic, before watching as he escapes with Tails and the Tornado. Metal Sonic orders the Tornado to be shot down, only to realize that Sonic had destroyed all of his cannons on purpose. Despite loosing Sonic, Metal Sonic proclaims that he has won, as he knows that Eggman is alive while his rival has gained nothing. Back at the Resistance headquarters, Sonic discusses his findings with Amy, Knuckles and Tails, and the four of them consider looking through Eggman's old files to find what plan he had yet to finish. Meanwhile, Metal Sonic and the Egg Fleet begin to launch an attack on Angel Island.

Trivia

 * Metal Sonic's Neo Metal Sonic form is based off of the form of the same name seen in Sonic Heroes.