Metal Sonic (メタル・ソニック Metaru Sonikku?) is an evil robotic version of Sonic created by Dr. Eggman. He first appears in Sonic the Hedgehog CD, with orders to go back in time and change the past so that Dr.Eggman can rule the future. Sonic must race him in Stardust Speedway to free Amy Rose. He returns in Knuckles' Chaotix, where he attempts to obtain the Chaos Rings, but he is stopped by the Chaotix. He has continued to make appearrances as an antagonist in the series throughout the years. He possesses a laser cannon built into his abdomen and a force field device. He usually only communicates with a series of electronic noises.

GameDaily placed Metal Sonic 13th on their "Top 25 Video Game Robots" list, describing him as Dr. Eggman's "greatest creation" and praising the strength of his abilities.[14]