(Japanese: 決勝戦！最強ライバル対決！！The Finals! The Strongest Rival Showdown!!) is the 138th episode of the Sun & Moon series, and the 1,077th episode of the Pokémon anime. It first aired in Japan on September 8, 2019.
Ash greets his mother, Mimey and Professor Oak as their ship arrives at Manalo Stadium. Delia congratulates her son on reaching the Manalo Conference finals. Oak admits they did come to cheer for Ash, but to also see Meltan. Ash promptly turns around to show his bag, and inside Rowlet and Meltan are sleeping. Oak takes Meltan and greets it with a pat on the head, though Meltan replies with a Flash Cannon after its sleep was disturbed. Suddenly, Meltan jumps off Professor Oak's hand, and starts spinning its nut, which emits sound waves. Oak examines it, realizing this is the odd behavior that has been mentioned in the reports. Out of nowhere, hordes of Meltan emerge from the sea and gather around Ash's Meltan. As the Meltan begin to dance together, Professor Kukui realizes that Ash's Meltan was calling to its friends. The odd display continues as the Meltan begin to create a strong electrical surge, and they eventually evolve into a single Melmetal. Oak explains that Melmetal has only ever been described in old books, but it has not been mentioned that it is an amalgamation of multiple Meltan. Rotom promptly photographs the discovery. Melmetal is clearly proud of its new power as it begins spinning and hitting the water with its hands. Kukui claims this could be a new move and settles on the name Double Iron Bash. Rowlet wakes up in shock to see Melmetal, but soon nestles in its friend's central chest cavity, With Melmetal now on his team, Ash leads his Pokémon into a cheer for the upcoming finals match.
The next day, Ash's friends sit among the audience, along with their Pokémon, anticipating an intense match. Kukui steps onto the battlefield, taking his position as the grand final round's referee. Ash sets his hat before stepping onto the field. As Ash followed by Gladion take their positions, Jīkyō recalls each of their paths to the finals. Meanwhile, Team Rocket settle in below their food truck to watch the match. Jessie remarks that she should've been in the finals, but Meowth admits that she went up against James earlier on. Jess then turns attention to James as he is putting the finishing touches to their latest mecha in time for the awards ceremony. The trio sneer and cackle as they imagine stealing all of the Pokémon at the Pokémon League. Back at Bewear's den, Bewear and Stufful exit the hot spring for another snack break. However, the Oranguru robot starts to malfunction.
Melmetal facing Silvally
Kukui, acting as the referee, announces the round rules - a three-on-three match. Delia has Mimey record the match on a camcorder. Gladion makes his first selection, his Silvally and Ash calls out Melmetal. Ash informs Melmetal that the winner will be the one who strikes first, so his Pokémon takes the initiative and rushes forward. Seeing Melmetal's confidence, Ash orders a Double Iron Bash. Melmetal flexes its muscles, and spins around to attack, and strikes Silvally on the second attempt. Ash calls for another Double Iron Bash, though Silvally combats the attack with an Air Slash and leaps to the side to avoid another hit. Melmetal spins yet again, so Gladion orders a Crush Claw. However, Ash calls for a Flash Cannon, which batters Silvally to the ground.
Pikachu facing Silvally
Gladion opts for another strategy by having Silvally moves in a zig-zag pattern to confuse Melmetal. The technique works as planned and Silvally manages to land a Crush Claw, leaving Melmetal reeling from the strike. Gladion then equips Silvally with a Fighting Memory, transforming it into a Fighting type. As Silvally approaches with a Multi-Attack, Melmetal responds with Flash Cannon. However, Melmetal's attack misses its mark, and it is knocked about by Silvally's attack. Melmetal regains its balance and attempts another Double Iron Bash. Silvally keeps its distance and lands an Air Slash on its opponent. Melmetal endures the hit and sends Silvally backwards with a second strike. Ash orders a Flash Cannon, and Melmetal follows through despite its visible exhaustion. Silvally lands its Multi-Attack first, while Melmetal's attacks suffers a delay before collapsing in defeat.
Pikachu facing "Lycanroc"
Ash recalls Melmetal before sending Pikachu onto the field. Pikachu rushes forward, though Silvally simply tilts its head to the side evade the Quick Attack. Ash orders a follow up Iron Tail, but Silvally catches the attack with its Crush Claw. Gladion calls for an Air Slash, which Pikachu narrowly escapes and enters into a Quick Attack to get away from his opponent. Silvally corners him, so Pikachu tries an Electroweb which fails. Pikachu launches another Electroweb and rushes towards it, using the added momentum to land a direct Iron Tail on Silvally. The surprising rebound knocks Silvally out of the match.
For his next Pokémon, Gladion sends Lycanroc. Ash braces Pikachu for its Counter, but is shocked when it uses Night Daze, a move Lycanroc cannot learn. Lycanroc rushes forward to attack and slashes through Pikachu's Electroweb with a Shadow Claw. However, the web only proved to be a distraction as Pikachu unleashes a Thunderbolt on Lycanroc. The attack reveals Lycanroc was only an Illusion as Mohn's Zoroark is fully revealed to everyone. Gladion calls upon his father's strength to guide him as he orders Zoroark to charge forward for another attack as the finals match continues.