Professor Oak contacts Professor Kukui's home to inform him, Ash, and Professor Burnet that yesterday's mysterious Pokémon is in fact a new species. Oak reveals that he has called it "Meltan", the Hex Nut Pokémon, and classified it as a Steel type. As Rowlet and the others indulge in some fruit, the Meltan that sneaked into Ash's backpack melts its way through one of Burnet's frying pans. By the time Rowlet scolds Meltan for this, it has already eaten the pan's base. Professor Oak wishes everyone well and signs off, prompting Kukui and Ash to prepare for the upcoming school day. As he does so, Ash hears strange noises coming from his backpack, but thinks little of it. After he and Kukui leave home, Burnet finds her ruined frying pan sitting on the kitchen counter.
At the Pokémon School, Ash reveals Oak's findings to his classmates. Excited, the others start scouring the classroom in search of another Meltan. Meanwhile, in the school's basement, Clefable is becoming increasingly tired from stopping the Meltan from eating all of the equipment. Back in the classroom, Kukui announces to his class that they will be battling each other. Kiawe is quick to challenge Ash, while Lana and Mallow pair up and Lillie is looking forward to battling Sophocles's Vikavolt. Ash tries to wake up Rowlet, but it appears to be in too deep of a sleep, so Ash leaves it inside his backpack for the day.
Later, Meltan attempts to wake up Rowlet. It resorts to spinning its hex nut head, which causes Rowlet to fly out of Ash's bag, though it resumes sleeping on a nearby balustrade. Meltan climbs up to Rowlet and tickles it, but Rowlet simply moves away and returns to sleeping. Meltan's glimmering hex nut also captures the attention of a wild Murkrow, who swoops down and grabs Meltan. Rowlet notices this missing and gives chase, eventually catching up, kicking Murkrow, and grabbing Meltan. However, it then realizes that Meltan's hex nut head is missing. Meanwhile, Team Rocket stops their doughnut van on the side of the road because of a technical fault. James inspects the van and finds the source of their issues, a broken nut. Just as Meowth wishes for a nut to fall from the sky, Meltan's hex nut hits him in the head. James replaces the broken nut with Meltan's, rendering the van operational again. Elsewhere, Rowlet tries to replace Meltan's nut with something suitable, but all of its candidates for a replacement are deemed unsuitable, prompting it to begin searching for Meltan's nut.
Over at the school, Kiawe and Ash's Triple Battle match begins. Ash's Torracat uses Fire Blast, which overwhelms Marowak's defense. Kiawe calls out his Turtonator to set the battlefield alight, but Lycanroc's Stone Edge breaks through the fire. Pikachu's Iron Tail collides with an Aerial Ace from Charizard. After the school bell rings, ending the match, Kiawe and Ash thank each other, and Kiawe then asks Ash what he will do now that he has completed all four of Alola's grand trials. Ash contemplates his answer and looks up to the sky, only to notice Rowlet fly by, so he quickly leaves to pursue it. In the Ultra Guardians' base, Clefable places the final Meltan in a basket case. As she is about to close the basket, she notices the Meltan eyeing the piece of metal in her hand. She quickly realizes the Meltan like metal.
After becoming tired, Rowlet lands on Team Rocket's van after smelling their Combee doughnuts. In the van, Jessie, irritated by the slow business, declares that she will search for the mysterious Pokémon, which they refer to as "Laser-Faced Metalheads", they encountered yesterday. James adds that he will inflict pain on the "Laser-Faced Metalheads" for destroying his precious bottle caps. Meowth asks how they will find the "Laser-Faced Metalheads", and Jessie suggests they just walk around. Meowth wishes that it would just fall from the sky, and on cue, Meltan lands directly on him. Meltan's tambourine falls into Wobbuffet's hands and he begins playing with it. The trio spots Meltan with one of their doughnuts as its head, and cannot identify it.
Soon Rowlet lands and begins eating Team Rocket's baked goods. Meowth is immediately infuriated by Rowlet's disrespect and jumps to grab it, but he instead lands in the van. As a result, Meltan's hex nut, which Team Rocket had put in their engine, flies out and reunites itself with Meltan. Team Rocket now recognizes Meltan as their menace. They quickly jump into their van for a quick costume change and perform a brief motto introduction. James keenly holds a net and tries to swipe Meltan. Rowlet grabs Meltan and flies into the air, it then uses Seed Bomb on James. The Everstone impact leaves James with an enormous bruise on his head. Rowlet lands on the ground again and says that it will defend its friend. Meowth is none too pleased and readies his sharps claws to attack. Rowlet flies into the air and sends out a barrage of Razor Leaves, but Meowth somersaults his way through the move. Meowth uses Fury Swipes, but Rowlet blocks the way and takes the hits. Rowlet is left scratched up and shivering from the pain. Meowth prepares to make the final attack, but Meltan jumps to Rowlet's defense. Its hex nut head breaks Meowth's Fury Swipes and it fires a direct Flash Cannon at him. Meowth is sent flying into the air and lands on top of James. Jessie also receives a Flash Cannon to the face. Stufful and its mother Bewear arrive on the scene. Bewear quickly tosses Wobbuffet and the others on to the top of the van, gently places Stufful in the driver's seat and promptly carries the entire van away.
Meltan turns its attention to Rowlet, and it is relieved that its friend is feeling well. Ash and Pikachu then arrive and quickly notice Rowlet's scruffy appearance. Meltan steps in front of Rowlet to defend its friend, but Ash is pleased to have encountered the mysterious Pokemon. Ash returns to the Pokemon School, and his classmates thank Rowlet for protecting Meltan. Just as Sophocles wonder how they will reunite Meltan with its friends, Clefable makes her way up to the classroom with several Meltan following her. She shows the class that she has tamed the Meltan by feeding them metal pieces, and the Meltan perform several acrobatic feats. Rowlet flies Meltan to its friends, but Meltan looks over at Rowlet. Mallow notices that Meltan is very attached to Ash's Rowlet, and it hugs Rowlet as a sign of their strong connection. Ash kneels down with a Poké Ball in hand and offers Meltan a place on his team. Meltan consults Rowlet first, and Rowlet pecks at the Ball to inform Ash that Meltan wishes to join them. Ash is thrilled and throws the Poké Ball at Meltan, but to everyone's surprise the Ball becomes wedged inside Meltan's hex nut head. Ash tries to catch Meltan again, and this attempt works. He performs a victory pose and calls Meltan out, and it quickly rushes to embrace Rowlet.