Metal Sonic is cool in every case. Do not @me on this.
This Metal Sonic was a unique exercise in mechanical design, which I commonly get carried away with when it’s present in a drawing.
The major design concept I built around was that of a fighter jet, with that category of the sense of aggressive and even violent speed. Elongated, sharp shapes, several air intakes, and wing-like extremities inform the overall sense of speed and power in the design.
The shape and color design borrowed a bit from Tails’ Cyclone jet also, which can be taken as a design attempt on Eggman’s part to mock Tails’ work as an inventor.