Metal Max Xeno takes place in the former location of
Tokyo Bay, now a desert referred to as Distokio by its inhabitants, approximately a century after the "Great Annihilation" in which the
supercomputer NOA attempted to destroy human civilization in order to prevent further ecological disasters. NOA is eventually defeated, but with its final moments it sends an order to its creations, colloquially known as "SoNs", to completely exterminate humanity, thus beginning a second genocidal campaign. The SoNs quickly began to overwhelm and destroy the remaining settlements in the Distokio area, leaving only a secret technologically advanced underground bunker called the "Iron Base" as the last surviving settlement. The Iron Base, which formerly served as the center of a post-apocalypse city known as Iron Town, is run by four survivors: D'Annunzio the base manager, Jingoro the head mechanic, Yokky, Jingoro's alcoholic protege, and Po-M, an android logistics officer. Iron Base is visited by a young man with a
metal arm (the
player character, default name "Talis"), who announces his intentions to destroy the SoNs with his
tank in revenge for their attack on his hometown and subsequent deaths of his mother and adopted father. The citizens of Iron Base agree to help him, in exchange for his assistance in seeking out survivors from the surrounding settlements. Talis finds no survivors in the ruined settlements, but, following an encounter with a large spider-like SoN, he rescues Toni, a former resident of Iron Town and the crush of Yokky, who had believed her to be dead. Yokky joins Talis in searching for survivors and the two encounter Dylan, the former leader of a bandit gang that had harassed Iron Town in the past, and save him from a tank hacked by the SoNs. He is taken back to the Iron Base, where he is reluctantly allowed to stay and recover, and Toni joins Yokky and Talis as they travel north to locate new survivors. The three encounter Misaki, an academic who wanders the desert in a
Flakpanzer Gepard searching for lost knowledge from before the apocalypse, and with their help he locates the entrance to a massive underground book repository guarded by Maria, the last surviving member of the repository's staff. After Talis assists Maria in destroying a group of SoNs besieging the repository, they, along with Misaki, move the books to Iron Base for safekeeping, and Maria and Misaki, along with a newly recovered Dylan, join the Iron Base as new residents. Following the operation, the team gathers for a small celebration. Yokky, noticing Talis' absence, excuses himself to search for him, and finds him in the midst of a painful
seizure. While trying to assist him, Yokky discovers Talis' body is almost completely cybernetic; Talis confides to him that it is the result of nanobots which allow him to use his metal arm as a weapon and heal damage to his body quickly, but at the price of him being turned into a machine by the nanobots, and that eventually he will no longer be "himself". Talis asks Yokky not to reveal his secret to anyone, but Toni overhears and becomes concerned for Talis, as she has begun to develop feelings for him. The next morning, Po-M reveals that data recovered from the library indicated the existence of "Cherbourg", a massive defense shield that could protect Iron Base from SoNs attacks. Cherbourg was being developed by an underground society called U-Tokio, but U-Tokio was destroyed following a failed operation to retake sectors of the surface from the SoNs, and Cherbourg was left uncompleted, its components scattered across the ruins of Distokio and U-Tokio. With Cherbourg, Iron Base would be able to adequately defend itself against attacks and rebuild Iron Town, so Po-M tasks Talis with recovering Cherbourg's components so that they may complete it. As they begin the search, they encounter an enormous SoN that Talis recognizes as the one that killed his mother and destroyed his home town. In a blind fury, he attacks it, but is defeated by a massive blast from the SoN and is brought back to Iron Base. Po-M nicknames the SoN "Catastropus" and identifies it as the one responsible for the destruction of the other settlements in Distokio, but warns that it is too powerful for Talis to confront at his current strength. Talis, frustrated, asks if there is anything to help him get stronger, to which Po-M has a possible solution in the form of Nephilim Technology: SoNs technology that was recovered and reverse-engineered by U-Tokio before its destruction, far more powerful than conventional weapons. Cherbourg is also NephTech, so she gives Talis a device that can detect its pieces, along with other components of NephTech weaponry to assist him in battle. While searching U-Tokio's tunnels for components of Cherbourg, Talis discovers a girl with a tail floating in a preservation chamber. Upon waking, the girl, named Ittica, goes with Talis back to Iron Base, and later reveals that she is a genetically engineered human-animal hybrid called a "Mute" which possesses the ability to shapeshift. Once all the components to Cherbourg are gathered, the team returns to base to assemble it. Toni confesses her feelings for Talis, but Talis turns her away, stating that he is aware of Yokky's feelings for Toni and does not want to hurt him, and reveals to her the extent of his body's conversion by the nanobots, stating that he does not have much time left. Yokky hears the conversation and, realizing Toni is in love with Talis, becomes conflicted about his self-confidence. Cherbourg is assembled, and successfully tested, but the test attracts the attention of the SoNs. Realizing that the SoNs are now aware of Iron Base's power, they track the source of the attacks to an abandoned military fortress formerly used by U-Tokio, now being used as a staging point and resource stockpile by the SoNs; after finding evidence of the Catastropus, they realize it has set its sights on the upgraded Iron Base. After shutting the fortress down to prevent the SoNs from using it, they return to Iron Base to prepare their next move. Yokky and Toni, with the assistance of Maria and Ittica respectively, come to terms with their feelings and insecurity, and the citizens of Iron Base steel themselves in preparation for the final battle. Aware that Catastropus is now en route, the team forms a plan: With Cherbourg in place, the Catastropus will be preoccupied attempting to break through it, and will leave itself unguarded for a close-range attack carried out by Talis and his team. With his team, Talis breaks through the Catastropus' vanguard and destroys the Catastropus itself, avenging his family and the people of Dystokio. Following the battle, Talis makes preparations to leave and seek out more survivors. Yokky joins him, and after getting a farewell from the citizens of Iron Base and a promise that they will always be a home for them to return to, the two depart in the tank Talis originally arrived in. After the credits, Talis and Yokky encounter Toni, who wishes to join them. After a moment of consideration, Talis smiles, and accepts her into the team. After the game, the player has the option of starting a
New Game Plus in two different modes: Story Mode, which replays the story with all player progression and items but locking certain plot-related vehicles and equipment, and Hunter Mode, which allows the player to start with all progression, vehicles, and equipment while minimizing the story, allowing the player to focus on hunting monsters and collecting bounties. == Characters ==