So, what is Fighting-type's role, really?
The Legendaries and Their Role:
Meloetta Pirouette Forme:
Meloetta's Pirouette Forme is representation of aggressive melody tunes, particularly those used in war music.
Swords of Justice:
Swords of Justice all revolve around chivalry and heroism, as they are based off The Three Musketeers. They are association with swords is a reference to their association with a "more civilized age".
Mega Mewtwo X:
Mega Mewtwo X is the physical counterpart to Mega Mewtwo Y. Because of this, they are bulging with muscles.
Buzzwole & Pheromosa:
Both Buzzwole and Pheromosa are alien, thus they are unnaturally stronger than their real-world counterparts.
Marshadow is based off a night marcher, Hawaiian ghosts of the fallen soldiers. Its signature move also references Hokuto no Ken.
The Trainers and Their Roles:(There are too many trainers so pictures will not be listed)
Bruno is the archetypal Fighting-type trainer, training in martial arts, wearing wrist weights, having an heavy Onix and constantly thinking about training and beating others. He has a soft spot for Rage Candy Bars, though.
"His Roaring Fists Do the Talking", Chuck is a black belt who became a married man. He tries to train all the day, but his glory days have long been over.
"A big wave in fighting", Brawly is a surfer who is also a bodybuilder. He used to train with Bruno to keep himself in shape. His Gym mimics the Granite Cave.
"The Barefoot, Fighting Genius!" Maylene is a martial arts prodigy who inherited a Gym from its unknown previous owner. Her father is a gambler. Due to this, Maylene trains hard to succeed, which makes her very hungry.
A pupil of the (former) Champion Alder, Marshal represents a future look to Cheren, after he completes his character development... or would have if Cheren didn't chose a different path. Marshal seeks strength as the only way of realizing ideals, thus he constantly tries to improve himself and seek new challenges.
"The Evolution fighter!", Korrina is the successor of Mega Evolution guru, Gurkinn, her grandfather. Korrina is also a PR video star, and dresses in outfits. Her legs are strong enough to break rocks by kicking.
Hala is the Kahuna of Melemele Island. He gives the player his/her starter, and teaches him/her some of the basics of the early game. In the post-game he helps Guzma gets his mojo back, and is implied to be his original kahuna.
Fighting-type Legendaries are generally associated with warfare in some manner or other. This is due to the fact that most of the deities in most mythologies are more focused on warfare than body-building or martial arts. However, most of Fighting-type legendaries are not based on deities, but sprites or literary figures.
In terms of Fighting-type trainers, all of them are training to better themselves and are open to new challenges.In fact, only Hala is not actively training to better himself. Everyone else is either a pupil of another trainer, or can self-train. Most of them are very confident due to their passion and their strength, though Bruno is more reserved and Maylene is the opposite of the stereotype.
Fighting-type has been showcased with trainers in all generations, but despite this does not enjoy a wide range of Legendaries. Until we see more Legendaries, we can't say what awaits the type.