Sonic facing Metal Sonic.
Sonic Triple Trouble
Near the start of Act 3, the player will receive the Rocket Shoes/Hyper Heli-Tails power-up and travel down a long corridor. Whilst traveling down the corridor, Metal Sonic will appear behind the player and knock them to the floor, at which point the battle will begin.
Metal Sonic has a rather basic attack pattern; he flies from either end of the screen, diving towards the player in an effort to attack. This moment is when the player has a chance to attack him.
After Metal Sonic has been hit four times, he uses the V. Maximum Overdrive Attack to dash across the bottom of the screen and attack the player, repeating the process after dashing six times. Once Metal Sonic has been hit twelve times, he will be defeated and slowly fly away, allowing the player to progress into last bosses in the game.