- For other robotic versions of Knuckles, see Mecha Knuckles.
In Sonic R, to unlock him, the player needs to collect all 5 Sonic tokens in Reactive Factory, finish in at least 3rd, then beat him in a one-on-one race. Sonic Channel featured a Japanese profile of Metal Knuckles. Translated, it states,
"As with Sonic, Eggman prepared this secret weapon for the sake of overthrowing Knuckles, considering his existence to be a hindrance. Having the same power plant as Metal Sonic, speed and acceleration power are high, but like Knuckles, this robot can glide from high places."
Appearance requirements: Collect 5 tokens in Reactive Factory in Grand Prix mode and finish better than fourth place to begin a one-on-one match with Metal Knuckles. Win this race and Metal Knuckles will become a possible choice on the character select screen.
- Low turning ability. To turn without losing control, the player must decelerate.
- Due to inertia, traveling on water is possible. Falling in the water may cause Metal Knuckles to become confused.
- From a high place, aim at a shortcut without pausing.