Mega Gyarados's fantastic Attack stat, solid defenses, and great offensive typing make it a strong wallbreaker against defensive Pokemon such as Gholdengo, Landorus-T, and Moltres. Its typing before and after Mega Evolution provides it many setup opportunities for the hyper offense teams it belongs on, especially when combined with Intimidate. It performs particularly well against threats such as Urshifu-R and Great Tusk prior to Mega Evolution and against Hisuian Samurott and Gholdengo after Mega Evolution. Mold Breaker allows Mega Gyarados to break past Dondozo, Dragonite, and Terapagos more easily, enhancing its wallbreaking capabilities. However, Mega Gyarados faces competition from other Dark-types such as Kingambit and Hisuian Samurott, since they are typically more consistent for hyper offense teams, with the latter providing valuable Spikes support for its teammates. Substitute blocks status moves such as Thunder Wave from Gholdengo and Slowbro or Toxic from Alomomola, turning all three into setup fodder; it also limits revenge killing efforts from Mega Lopunny and Raging Bolt. Earthquake allows Mega Gyarados to cleave straight through Toxapex, Raging Bolt, and Melmetal, preventing them from trading with it safely. Taunt shuts down opposing setup from Pokemon such as IronPress Zamazenta, as well as preventing entry hazards from going up from Ferrothorn and defensive Garchomp. Similarly to Substitute, it also shuts down status conditions such as paralysis and Toxic poison from defensive Pokemon such as Slowbro and Gliscor.

While it has a decent defensive profile, Mega Gyarados's lack of longevity means it primarily fits on hyper offense teams that want to capitalize off of its power and unique ability to break past stall teams with ease while not being slowed down by Dragonite and Terapagos due to Mold Breaker. Mega Gyarados usually works best mid-game, helping to overwhelm defensive staples such as Ferrothorn, Toxapex, and Clefable; this is heavily appreciated by offensive teammates such as Ogerpon-W, Kingambit, and Dragonite. Specially offensive partners such as Gholdengo, Volcarona, and Raging Bolt can support Mega Gyarados in taking down these physically defensive foes, while Mega Gyarados does well against opposing specially defensive walls such as Moltres and Ting Lu. Suicide leads are necessary on the hyper offense teams that Mega Gyarados belongs to. Landorus-T and the more niche Glimmora can set up entry hazards to assist in Mega Gyarados's wallbreaking capabilities; for example, by letting it OHKO Serperior with boosted Crunch after Stealth Rock. Dual screens leads such as Tapu Koko and Grimmsnarl improve Mega Gyarados's longevity and bulk, notably letting Mega Gyarados survive +1 Garchomp's Devastating Drake with Reflect, allowing it more opportunities to set up. All of these suicide leads can deny opposing Stealth Rock from going up with either Taunt or Mortal Spin, which makes up for base Gyarados's weakness to Stealth Rock. Although Mega Gyarados has Dragon Dance, it is still prone to being revenge killed by faster Choice Scarf Pokemon such as Tapu Lele and Urshifu-R due to its mediocre Speed, making teammates such as Gholdengo and Dragonite, which can punish these revenge killing attempts, valuable partners.