The game starts out with Sonic, Tails, and Knuckles tracking a Chaos Emerald. They soon find out it has been stolen by a group of thieves riding hoverboards. Sonic tries to stop them, but they simply go around him. Knuckles manages to knock one off his board, but he hitches a ride with one of the others. Tails spots a strange marking on the board, but then Sonic ignores him, takes the board and gives chase. He soon catches up with their leader, but as Sonic cuts in front of him, the mysterious thief attacks him from above and knocks Sonic off. He mutters "So you're supposed to be the fastest thing alive?" before escaping.
The next day, Sonic and friends find out that Eggman is hosting the EX World Grand Prix, a tournament for Extreme Gear. What's more, is the mysterious thieves from the night before are competing. So Sonic and friends decide to enter to find out what Eggman is up to, and who these thieves are.
The stage takes place at day time, the city also called "Future City." There are many 'future' cars that must be avoided unless you are a Power Type Character. Everything in the city is metal, and all metal streets have 'future' buildings. There are three grinding rails for speed type, two air ride links for flying type, and outnumbered obstacles to smash for the power type. The stage in Story Mode is only playable as Sonic, but in a normal race, any character is available.
In Sonic Free Riders, the Metal City is the last stage. The stage appears in the Last Story scenario, having two difficulty modes: standard and expert.
- On a picture in the city, Sonic is shown from the art in Sonic Heroes. There is also a picture of Sonic running away from a Killer Whale in Sonic Adventure.
- It is possible to get more than 30 tricks performed in one lap on this course.
- The Track was based on Mute City, from the F-Zero Racing series.
- In Sonic Generations 3DS, Metal City appears in 2 profile card patterns.