The Metal Carrier is the boss of Sky Fortress Zone in Sonic the Hedgehog 4: Episode II, and it is also seen in Act 1 of Sky Fortress Zone. As its name implies, it is a aircraft piloted by Metal Sonic.
The Metal Carrier is a long, single-seater aircraft. The craft has hangers that contain Balkirys that Metal Sonic can use to try and attack the player. The aircraft can also shoot energy blasts that fire in a set place. The craft also contains a small cannon that can shoot out black cannon balls that the player can rebound back into Metal Sonic with the Spin Jump. In the boss battle, Metal Sonic's aircraft demonstrates the ability to shoot powerful laser beams.
The aircraft is first encountered in Sky Fortress Zone, Act 1, where it appears several times to attack the player, during this time, Metal Sonic will send out Balkirys to attack the player shoot out energy blasts from the aircraft. Near end of the Act, Metal Sonic will fire several cannon balls at the player, Sonic can then damage the Metal Carrier by rebounding the cannon balls fired from the aircraft into Metal Sonic. After a certain amount of time has passes, Metal Sonic will get distracted and crash into the Sky Fortress, forcing him to flee, however, if the player hits Metal Sonic enough times during this segment, the Metal Carrier will get damaged, causing the aircraft to fall, doing so will award the player with an achievement/trophy.
The Metal Carrier returns as the boss battle for Sky Fortress Zone. During the battle, Metal Sonic will fly the craft upside down and fire lasers at the player, the player must avoid these lasers and attack Metal Sonic. The laser typically fire in a pattern such as firing all four lasers in canon or firing two lasers at the same time. Metal Sonic is unreachable if he moves underneath the Tornado. Once Metal Sonic has received enough hits, Metal Sonic will pilot the aircraft directly in front of the Tornado and fire laser directly in front of the player whilst sending out Balkirys to disrupt the player's movement, the player must once again try to attack Metal Sonic whilst avoiding these obstacles. After a certain number of hits, Metal Sonic will try to flee, at this point, missiles from the Sky Fortress will fire at the player, is the Tornado is hit by these, they will push the player off the edge of the screen, costing them a life. The player must avoid these missiles and use the Tornado's Tornado Boost Tag Action to hit Metal Sonic one last time, defeating the aircraft. After the aircraft is defeated, Metal Sonic will jump out of the craft as it explodes and flee to the now heavily damaged Sky Fortress, where the player pursues.
- The sequence where the Tornado must dodge the Metal Carrier's lasers is akin to the final battle in Sonic Rush, where Super Sonic and Burning Blaze avoid lasers from the Egg Salamander in order to reach the boss itself.
- This is one of the few instances in the series where Metal Sonic fights his enemies with a machine under his control, rather than fighting the heroes directly.