Roy Mustang learned his Alchemy from Riza Hawkeye's father. He was his teacher, and taught his flame alchemy. Roy Mustang believed that with this power, he could help people, save people. When his teacher found out he wanted to join the military, he was displeased, but still agreed to teach him the strongest alchemy he knew as long as Roy's intentions for using it were for good. Though before he could explain more, Hawkeye's father died from a health condition. Though he left all Mustang needed to know with his daughter Riza. His method of keeping this information with her was with markings on her back. Before Riza's dad died, he asked for Mustang to look after her.
Like other State Alchemists, Roy was sent to Ishbal to raze the region, for the Army could not subdue this area. Mustang was 23 at this time. During these events he ran into Maes Hughes as they reminisced about the past and why this war started, they were ambushed by Ishballen people, but were saved by a sniper. The sniper was later revealed to be Hawkeye. During this "Massacre", Roy has a very negative view of things. He felt like a killer, like a murderer, when his only intentions were to help people, not take their lives. Only Later to realized that he was protecting his men, his allies, his friends from being killed themselves. So then on he made a goal to become the Fuhrer, to stop meaningless wars, and to help people like he wanted to do. So he surrounds himself now with his most trusted friends. He told Hawkeye that if ever strayed from his goal, that he ever started to change, to want power more than the greater good, to kill him. That was an order.
Outwardly arrogant and playfully manipulative, Mustang is extremely intelligent and adaptable. Roy was seen as ruthless careerist, and a womanizer at the beginning of the series, but as in went one, his character really adapted. He became paternal Commander who cares about his men's emotional and physical well being. he would put their lives before his own at any moment. While he is haunted by the tragedy that was The Ishballen War, and the Innocent civilian lives he took, although he was still thanked by his co-workers for saving their lives time and time again.
Alchemy, and Fighting Style
As powerful as Mustang is with Alchemy, he uses gloves that have a transmutation circle imprinted on them, and they are also made from a fabric called "pyrotex/ignition cloth", which lets him make fire from a spark that is created from snapping his fingers. He then uses his alchemy to manipulate the gases in the air, in order to uses flames the way he wants, anyway he wants. Though Oxygen isn't combustible, he inflames the Hydrogen in the air. Though Mustang is often considered useless on rainy days.