A group of Meltan first appeared in Evolving Research!, where they were briefly seen underwater, walking away from a Mystery Box near Poni Island.
Even more Meltan appeared in A Grand Debut!, where they were briefly seen on the boat Ash, his classmates, and Professor Kukui were taking from Poni Island to Melemele Island.
All of the Meltan reappeared in Show Me the Metal!, where they caused havoc on Melemele Island. While investigating the sewers, the Meltan were divided into two groups. One group ended up at the Ultra Guardians base and ate some machinery before being stopped by Lusamine's Clefable. Afterwards, they ended up at the Pokémon School, where they were discovered by Ash, his classmates, and Professor Kukui. Unable to recognize what the Meltan were, the group determined they were a new species and decided to study what they work on and how they worked. During the experiments, Kiawe's Marowak accidentally scared the Meltan off with the flames on its bone, forcing Ash and the others to search for them. Meanwhile, the other group of Meltan ended up at Bewear's den, where they ate most of James's bottle cap collection, infuriating him. Team Rocket chased the runaway Hex Nut Pokémon into some nearby woods and attempted to capture them. The Meltan retaliated with a combined Flash Cannon, only for Bewear to block the attack and scare the Meltan away.
While Ash and the others searched, a single Meltan stayed behind, where it met Ash's Rowlet. After Rowlet helped rescue its hex nut from a wild Murkrow, the Meltan took a liking to Rowlet. Afterwards, the Meltan group at the Pokémon School called the other group to their position, reuniting them all except for the Meltan bonded with Rowlet. It instead chose to follow Rowlet back home by hitching a ride in Ash's backpack.
In Got Meltan?, Ash caught the Meltan that befriended Rowlet. The other Meltan were tamed by Clefable, who started using scrap metal to feed them as a reward for following instructions. In Beauty is Only Crystal Deep!, they helped deliver a box containing Beast Balls and a medical kit to the Ultra Guardians for their next mission. Clefable then fed them screws as a reward.
In SM124, the Meltan appeared helping the Ultra Guardians again. They were also revealed to have started multiplying, doubling the total number. In SM126, the Meltan were shown to have multiplied even further, bringing the total number to 60.
In the Poké Problem segment for SM133, the Meltan left the Ultra Guardians base after overhearing Ash's Meltan contacting them from Manalo Stadium. In SM137, the Meltan arrived at Manalo Stadium.