Well, I think you could have done a little bit more work.
Try:
1. Changing the background every once in a while, I thought that at the part when metal sonic boosts, once he goes off the screen he teleports to the left side of the screen and keeps going right.
2. Making it play once, it looped for about 20 times while I was writing this.

u could have done better

I like the sonic/metal sonic rivalry, but there's almost no true action and the battle is too quick. have some more action, okay?