Metal Sonic is the sixth boss of Sonic the Hedgehog Triple Trouble, making a surprise appearance as a sub-boss in Atomic Destroyer Zone Act 3. Although their race / battle in Stardust Speedway Zone during Sonic CD is much more well known, Sonic (or Tails) and Metal Sonic clash once again inside the Doctor's titanic superweapon.
Just before the fight begins, the player will come across a Monitor containing either the Rocket Shoes or Hyper Heli-Tails depending on the player's character, and will begin flying through a long corridor. After flying for a few seconds, Metal Sonic appears behind Sonic/Tails and ambushes him with his Maximum Overdrive Attack, knocking him out of his flight. Afterwards, the fight begins.
Metal Sonic's first attack is to fly back and forth across the screen, diving at the player to attack. While Metal Sonic is doing this attack, the player must jump up and hit him with a Spin Attack. For every four hits scored, Metal Sonic will swoop along the floor with his Maximum Overdrive Attack, becoming invulnerable to harm. The player must continually jump up and down to avoid the Maximum Overdrive Attack until it stops after doing it six times. After 12 hits, Metal will be critically damaged and retreat, allowing the player to progress to a teleporter that takes them to a Marker, followed by the final battle with Eggman himself...
First Metal Sonic chases Sonic...
...and eventually catches up
and so begins a Sonic vs. Metal Sonic fight.