By Leveling Up:
* Fire: Ember, Flamethrower, Fire Blast, Heat Wave, Will-O-Wisp, Overheat, Flame Charge, Fiery Dance, Lava Plume, Sunny Day
* Flying: Peck, Drill Peck, Air Slash, Sky Attack, Brave Bird, Hurricane, Tailwind
* Other: Ancient Power, Endure, Roost, Agility, Quick Attack, Aerial Ace, Feather Dance, Defog, Substitute, Nasty Plot, Heat Wave, Solar Beam
By TM/HM:
* Fire: Fire Blast, Flamethrower, Heat Wave, Will-O-Wisp, Overheat, Flame Charge, Lava Plume, Sunny Day
* Flying: Fly, Aerial Ace, Brave Bird, Hurricane, Tailwind, Roost, Defog
* Other: Aerial Ace, Sunny Day, Substitute, Roost, Thunder Wave, Toxic, Thunder, Protect, Reflect, Light Screen, Hidden Power, Flash Cannon, Aerial Ace, Sludge Bomb, Shadow Claw, Earthquake, Facade, Brick Break, Aerial Ace, Roost, Will-O-Wisp, Thunder Wave, Thunder, Toxic, Protect, Reflect, Light Screen, Hidden Power, Flash Cannon, Sludge Bomb, Shadow Claw, Earthquake, Facade, Brick Break
By Breeding:
* Fire: Flamethrower, Heat Wave, Will-O-Wisp, Overheat, Flame Charge, Lava Plume, Sunny Day
* Flying: Fly, Brave Bird, Hurricane, Tailwind, Roost, Defog, Aerial Ace
* Other: Ancient Power, Endure, Roost, Agility, Quick Attack, Aerial Ace, Feather Dance, Defog, Substitute, Nasty Plot, Heat Wave, Solar Beam
By Move Tutor:
* Fire: Heat Wave, Will-O-Wisp, Overheat, Flame Charge, Lava Plume, Sunny Day
* Flying: Fly, Brave Bird, Hurricane, Tailwind, Roost, Defog, Aerial Ace
* Other: Ancient Power, Endure, Roost, Agility, Quick Attack, Aerial Ace, Feather Dance, Defog, Substitute, Nasty Plot, Heat Wave, Solar Beam, Hidden Power, Thunder, Toxic, Protect, Reflect, Light Screen, Flash Cannon, Sludge Bomb, Shadow Claw, Earthquake, Facade, Brick Break
Signature Move:
* Sacred Fire (only in Pokémon Scarlet and Violet)
This is not an exhaustive list, but it should give you a good idea of the moves Moltres can learn. Keep in mind that the availability of specific moves may vary depending on the game and generation.