Now the answer may seem obvious, but hear me out. In all his bios/descriptions, he's been stated to be an exact copy of Sonic in all his abilities. But when seen in-game, he's been shown to generate energy fields around him, and fly. On the other hand, he has never been shown to curl up into a ball and spindash (CORRECTION: he can spin in SA2 and Sonic Rivals 2, but given his spike shape, it does not make much sense), or jump around like Sonic (because of his flight). Because of this, I don't think he's an EXACT clone.
I figure he can clone Sonic's speed and agility through his flying (he can most likely dodge as fast as Sonic, and who needs jumping when you can fly?), and the spin-dashing could be something Sonic has on Metal.(vice versa for Metal's flight).
Thoughts?