A Metallix is a robotic version of Sonic the Hedgehog - the original model carried the title of the Metal Sonic. The first was only one part of an elite Brotherhood of Metallix. As fast as Sonic himself, and armed with a lethal death ray, Metallixes are notably very difficult to kill, their only apparent weak spots being in their necks.
The Sonic Terminator
The first Metallix appeared in the adaptation of Sonic the Hedgehog CD. The robot, programmed solely to match and kill Sonic, used the terraformed Miracle Planet as a power source. It was mainly designed by Grimer.
It captured Amy Rose in order to lure Sonic into a trap, fighting him to a standstill; it then took Amy to the Miracle Planet to lure Sonic there, where its bond to the planet made it nigh-invincible. Not even ramming it after running around the entire planet could do any damage. However, Sonic was given the Time Stone by a time-travelling Sonic from the future, enabling him to travel back in time to prevent the planet's cyberforming and thus erase Metallix from existence... and then go give the Time Stone to himself from the past. (How this time conundrum works at all has been debated, and even artist Richard Elson is confused by it 
Brotherhood of Metallix
Doctor Robotnik would later convert his old Egg Fortress base in the Special Zone into a Metallix factory, intending to leave the robots there to create the ultimate Metal Sonic. As a safety precaution, he built a self-destruct program into their design.
The Metallixes secretly went rogue, calling themselves the Brotherhood and building a Emperor Metallix as they plotted to conquer Mobius themselves. The Brotherhood were primarily made up of multiple versions of the first Metallix, acting as drones and footsoldiers. This didn't make them any easier to destroy however, as one was seen to still function, even with a gaping hole in the middle of its chest after Knuckles impaled it with a girder.
Sonic and Robotnik ended up making an uneasy alliance to stop the Brotherhood once and for all, resulting in Sonic using the remote to activate the self destruct program, deactivating the Brotherhood forever.
- Metallix Emperor
- Metallix Mark 2 (Mecha Sonic)
- Metallix Mark 3 (Knuckles Metallix)
- Porker Metallix
- Neo Metallix
- Shadow II's Metallix shell
This list relates to the original design of Metallix. For appearances by the other models, see their respective pages.
- Issue 22 - Girl Trouble
- Issue 24 to Issue 28 - The Sonic Terminator
- Issue 52 - pin-up
- Issue 54 to Issue 58 - Total Chaotix
- Issue 57 - pin-up
- Issue 59 to Issue 62 - The Brotherhood of Metallix
- Issue 67 to Issue 72 - The Return of Chaotix
- Issue 79 - Return to the Miracle Planet (actually a civilian in disguise)
- Issue 114 - pin-up
- Issue 129 - Robotnik Reigns Supreme
- Issue 130 - Showdown
- Issue 149 - pin-up
- Issue 189 - pin-up
- Issue 227 - R.B.R
- Issue 229 - The Syndicate
- Issue 243 - pin-up
- Issue 250 - pin-up
- Issue 255 - pin-up
- 15th Anniversary Special - The Elephant in the Room and pin-up
- Sonic the Summer Special 2009 - Brotherhood (actually Doctor Robotnik Appreciation Tribe in disguise)
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- [http://groups.yahoo.com/group/sonicthecomic/message/12742 Yahoo! Groups