Gyarados is a terrifying sweeper due to its combination of Dragon Dance and Moxie letting it snowball through weakened teams after it gets a KO. Its stellar typing allows it to pivot into Ground-type moves and set up, while bluffing a Mega Gyarados set. However, its crippling Stealth Rock weakness alongside a poor initial Speed tier means it struggles to find setup opportunities against a lot of teams. Bounce in conjunction with Flyinium Z allows Gyarados to OHKO erstwhile switch-ins like Grass-types such as Tangrowth, Tapu Bulu, and Amoonguss, which Gyarados lures in. Earthquake allows Gyarados to break through Toxapex easily and reliably stop Magnezone, Mega Mawile, and Tapu Koko from revenge killing it. Power Whip is another option that allows Gyarados to break past Slowbro, Rotom-W and Tapu Fini efficiently, although it is generally inferior to Earthquake due to Gyarados struggling to break past Toxapex, and Power Whip's main targets can be chipped into Earthquake range easily.

Gyarados fits best on hyper offense teams because it often struggles to find multiple setup opportunities, and its reliance on its Z-Move to break through defensive checks means it needs a lot of support from its teammates to clean late-game. Dual screens setters such as Tapu Koko and Grimmsnarl give Gyarados many more setup opportunities than its mediocre bulk otherwise allows. Pokemon that can wear down Gyarados's checks, including bulky Grass- and Flying-types such as Corviknight, Zapdos, and Tangrowth, such as Mega Garchomp and Serperior are great partners. Mega Garchomp in particular is exceptional due to providing an Electric immunity to cover Gyarados's most crippling weakness, as well as greatly appreciating Gyarados luring in bulky Grass-types such as Tangrowth for it. Lastly, leads that deny or remove entry hazards such as Mega Diancie and Excadrill are extremely beneficial to help Gyarados's crippling weakness to Stealth Rock. Taunt users such as Hawlucha, Tapu Koko, and Grimmsnarl are other examples, and they can deny Pokemon like Toxapex recovery to force damage on them.

Mega Gyarados's high Attack stat, good offensive typing after Mega Evolution, Dragon Dance, and great ability in Mold Breaker make it a threatening sweeper. Mold Breaker lets it ignore abilities of Pokemon such as Unaware Clefable and Quagsire and Storm Drain Gastrodon, which would normally check it with ease. Mega Gyarados's good typing and base ability Intimidate grant it many setup opportunities to set up with Dragon Dance against foes like Heatran and Mega Scizor and clean late-game. Waterfall neutrally hits Pokemon such as Clefable, Tapu Koko, and Corviknight, and its flinch chance lets Mega Gyarados bypass some of its checks. Crunch hits Water-resistant Pokemon such as Tangrowth and Mega Latias. Substitute offers Mega Gyarados temporary status immunity and lets it avoid Scald burns and Toxic poison from foes like Toxapex, Blissey, and Alomomola. Taunt prevents Pokemon such as Toxapex from removing Mega Gyarados's boosts with Haze and allows it to avoid status from Will-O-Wisp Rotom-W and Toxic Heatran. Earthquake hits Toxapex, Hydreigon, and Rotom-W hard.

Mega Gyarados works best on hyper offense teams. Since it often struggles to find opportunities to set up and gets chipped too easily, dual screens support from Tapu Koko and Grimmsnarl is extremely beneficial. Entry hazard support from dedicated hyper offense leads such as Landorus-T, Excadrill, and Mew wears down Mega Gyarados's checks such as Tangrowth, Toxapex, and Alomamola. Rillaboom, Hawlucha, and Serperior assist Mega Gyarados against faster teams and benefit from it beating bulkier teams. Due to its middling Speed and subpar defensive typing, Mega Gyarados is very vulnerable to being revenge killed by faster Pokemon such as Kartana, Rillaboom, and Hawlucha, so checks to them such as Volcarona, Thundurus-T, and Kommo-o are imperative. Hawlucha is an exceptional partner, as it appreciates Mega Gyarados dealing with bulkier teams and pressuring Zapdos and Toxapex.