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 Dr. Eggman is hosting the EX World Grand Prix, a tournament for competitive Extreme Gear racing. They discover that the mysterious thieves from the night before are already competing in the tournament so Sonic and his friends decide to enter to find out what Eggman is up to and who these thieves are.
This futuristic course takes place at day time. There are many futuristic-looking cars that must be avoided unless the player is using a Power Type character who can smash them away. Everything in the city is metal, and all metal streets have 'future' buildings. There are three grinding rails for Speed Type riders, two Air Ride routes for Fly Type riders and outnumbered obstacles and barricades to smash for Power Type characters. The stage in Story Mode is only playable as Sonic, but in a normal race, any character can be used.
In Sonic Free Riders, Metal City is the last course. The stage gets unlocked by clearing the "Final Race" scenario of the World Grand Prix and has two difficulty modes: standard and expert. This course is also used as the setting of the tutorial lessons in the game.