This is the tragic story of Sonic... Sonic the Swordsman
One day, Eggman developed another plan to catch his enemy Sonic and so he developed "Mekkaku Sonikku" (Metal Sonic's name in the series.
Mekkaku's first mission was to catch Amy, Sonic "Wannabe" Girlfriend, to trace Sonic right into his trap. His plan was devided into 3 phases: Get Sonic on the Secret Planet, which is reapearing every 3 month (check Sonic CD), make Mekkaku catch Sonic, get off the planet as soon as possible.
While Super Sonic was rushing through space, Eggman dumped Mekkaku Sonikku and starts to develope "Mekkaku Ver. 2", but he he would never guess, that Mekkaku developed an ego of it's own and returned... more dangerous than ever.