Roy Mustang is the "Flame Alchemist," having absolute control over heat and fire through alchemy. Using special gloves that create a spark when he snaps his fingers, Roy can create anything from a tiny ember to burn a letter, to a raging inferno that can destroy a humanoid body in seconds. His precise control over the alchemically enhanced flame is so accurate that he can boil the water in a persons' eyes and can also attack enemies amongst a riot without hurting any allies.
Outwardly arrogant and playfully manipulative, Mustang is intelligent and almost always one step ahead of his opponents, and likes to feel in control of the situation. He is one of the superiors of Edward Elric. On the surface, he appears to be nothing more than a man of the military who pursues promotions and praise and is considered a ladies' man who constantly goes on dates with different women. Mustang's true goal is to become Führer in order to gain the power to reform the government in order to absolve his sins in the Ishval War as well as change the country for the better, along with the joking requirement for female officers to wear tiny miniskirts (which considerably increased Havoc's loyalty to him and caused Hawkeye to be angry with him).
His goals are admirable enough that he earns the fierce loyalty of his good friends Lt Col. Maes Hughes, Major Alex Louis Armstrong, and his own subordinates, among whom are Riza Hawkeye, Jean Havoc, Heymans Breda, Vato Falman, and Kain Fuery. While Mustang has a close and amicable relationship with all of his subordinates, he appears to share a deeper bond of affection with his second-in-command Riza Hawkeye, who has devoted her life to supporting him. This bond culminates in the final episodes of the anime when Mustang chooses Hawkeye alone to accompany him on his greatest and most dangerous mission.
Though a hero of the Ishval War, he remains haunted by the horrors of war and suffers great remorse for the lives he took.
After the Promised Day arrives, he is forced to open the gate by Pride and Wrath, they first try to make him do it voluntarily by reviving Hawkeye, but he refuses. So Pride opens the gate for him using his Philosopher's Stone. Mustang gains the power to transmute without a circle, however his price is his eyesight.