Captain Metal, formerly known as Metal Sonic v3.3, is the fourth robot in a line of Metal Sonic robots created by Dr. Eggman. After being destroyed by Shadow, Blaze, and Marine in the Sol Zone, Metal Sonic was rebuilt and renamed Captain Metal. Now the leader of Blackguard Pirates, Captain Metal seeks the Sol Emeralds as part of his grand scheme.
Shortly after the destruction of both Metal Sonic v3.2 and Metal Scourge by the Suppression Squad, Eggman created Metal Sonic v3.3 model, this time using the newer SXSU-401 engine, allowing the robot to transport to any other dimension to pursue Sonic. Metal Sonic then left for Moebius against its creator's will to find and attack Sonic and the others in Castle Acorn. Sonic later made an offer for Metal Sonic to help him take out Scourge first, instead of attacking everyone else and getting nowhere. The robot nonchalantly agreed. Though, Scourge did not give up. He rushed to the throne room, followed by Sonic and Shadow. Scourge turned the tables on everyone, claiming he placed Anarchy Beryl in his throne. This managed to turn Scourge into a stronger form; Super Scourge.
Metal Sonic was temporarily defeated by Super Scourge along with the others. After then deducing that defeating Scourge was no longer an option it then tried to attack Sonic again. It was later transported to another location along with Shadow when he tried to override Metal Sonic's teleporter engine with Chaos Control. Arriving in an alternate universe (the zone of Sonic X), Metal Sonic was employed by that reality's version of Dr. Robotnik to attack everyone. Once it made its charge however, it was once again transported to a different reality by Shadow.
Metal Sonic and Shadow then after ended up in the Sol Zone, floating above an ocean. Shadow tried to convince Metal Sonic to no longer obey Dr. Eggman, but Metal Sonic completely ignored Shadow's request and kicked him into the water before flying off to look for the zone's version of Eggman. Furious that it could not locate that zone's Robotnik, Metal Sonic began attacking Southern Island. Shadow, Blaze and Marine showed up shortly to witness the destruction Metal Sonic had caused. Blaze furiously attacked Metal Sonic, but the machine simply used it's powers to reverse Blaze's attack. Neither Shadow or Marine could take down Metal Sonic. However, Shadow tried once again to convince Metal Sonic to work with him, but Metal Sonic simply pointed out they each had different goals, and its was to serve Dr. Eggman. Thus, Blaze set fire to Metal Sonic, and Shadow charged at him. The robot flew towards the Ocean Tornado, and Marine destroyed him with the ship's cannon.
After the main Metal Sonic was rebuilt into v3.7 onwards, he was upgraded to have the memories of all of his previous lives - including 3.3 - who unbeknownst to Eggman had survived to live a separate life of his own. Notably, the main Metal Sonic used his memories of being 3.3 in order to counter one of Shard's attacks.
Metal Sonic was found alive by the Blackguard Pirates' doctor: Doc Ratcheturn, who had gone out to salvage scrap metal, Metal Sonic turned out to be alive and killed Ratcheturn, using his ship to go to the Pirate's Island. Metal Sonic then challenged Captain Boltbeard to a duel and managed to defeat him easily, using Boltbeard's parts in order to upgrade himself into Captain Metal, becoming the leader of the Blackguard Pirates. At some point Captain Metal came into conflict with three other robotic pirates, who he reduced to heads and left them on sticks so that all they could do was talk. Captain Metal now had an army of robotic pirates, including his first mates: Swash and Buckle, and also a large robotic octopus named the Kraken. After the Super Genesis Wave had been put into effect, the Wily Egg landed in the Sol Zone, right beside Pirate's Island and was taken over by Metal and his crew, who upgraded it into the Egg O' War.
When Bean the Dynamite and Bark the Polar Bear later arrived in the Sol Zone from Mobius Prime, Captain Metal allowed them to join his crew. At some point, he also obtained the red Sol Emerald, which was the last Sol Emerald that Blaze had yet to recover. Drawn to it, Captain Metal began to make a grand plan for the red Sol Emerald, Blaze, and the other six Sol Emeralds in her possession. While in possession of the red Sol Emerald, Captain Metal never let it out of his sight.
At some point afterwards while sailing out on the seas, Captain Metal and his crew came across the Ocean Tornado, which carried Blaze, Marine the Raccoon, Amy Rose, Cream the Rabbit and Cheese, and the two parties engaged in a mid-sea battle with each other. In the midst of the battle, Captain Metal learned from Buckle that Blaze had infiltrated his ship, and ordered him to put him on loudspeakers. Assuming Blaze was hearing him, Captain Metal gave her the choice of surrendering herself within his time limit, or he would destroy the Ocean Tornado and kill everyone on board it. When her time ran out, Captain Metal was losing his patience, but then Blaze showed up. As introductions were made, Blaze demanded to Captain Metal that he surrendered the Sol Emerald and she would spare his crew. In response, Captain Metal used his ship's laser cannon to destroy the Ocean Tornado, as he revealed to Blaze that he lied about sparing her friends. With Blaze in despair and rage, Captain Metal proclaimed how his actions was justified, before warning to Blaze to stay in line for his plans as well. Watching as Blaze was knocked out cold by one of his crew members, Captain Metal noted how Blaze had let her emotions get the better of her, and voiced how his intended to make good of his second chance at life.
Captain Metal then took Blaze and his crew back to the Pirates' Island and proceeded to hold a meeting with his crew, revealing to Blaze his plan to use the Egg O' War to rule the seas and the skies. Amy, Cream, Marine, and the Sprockets arrived and saved Blaze from Metal and then Bean and Bark stole his Sol Emerald, Metal, in a rage, released the Kraken and sent his crew after Bean and Bark.
Captain Metal was further surprised when Johnny arrived to take the Sol Emerald, in barely controlled rage Metal cut off another pirates head before telling Buckle and Swash to prepare the Sub-Marine, to which they foolishly replied that they could not, receiving a blast from Metal, who then took the sub-marine to watch the seemingly invincible Kraken destroy his enemies, however, thanks to Bean's Behemoth Bomb. The Kraken's destruction did cause Whisker to drop the Emerald, which was then caught by Metal as he rose out of the water, insulting Whisker before revealing his enhanced Crab form.
As the three groups fire upon each other, Blaze attacks Metal in an attempt to retrieve her Emerald. Blaze tries to reason with Metal by stating that her world will die without the Emeralds keeping it stable. Metal simply replies that since the Egg O' War can move through dimensions, Blaze's world dying means nothing to him. Metal manages to defeat Blaze by shocking her and flies off with her unconscious body to the Egg O' War.
Metal straps Blaze to the Egg O' War's generator room and has it drain both her and the Emerald's to power it up. Blaze is saved just in time by Cream, Cheese, and Amy, who free her from the generator and distract Captain Metal long enough for Blaze to get the Sol Emeralds. Using the Emeralds' power, Blaze turns into Burning Blaze and destroys Captain Metal's body with her flames.
However, Metal reveals that he downloaded his mind into the Egg O' War's systems at the last second, effectively becoming the Egg O' War itself. He attempts to steal back the Sol Emeralds, but Blaze effortlessly stops him and blows a large hole in the Egg O' War, causing it to sink into the ocean. Although defeated, Captain Metal's eye lights up again as the Egg O' War rests at the bottom of the ocean, revealing that he is still alive.