What is Roy Mustang's alchemy?

Mustang is the Flame Alchemist — his specialty is fire. Specifically, he manipulates the oxygen-hydrogen ratio in the air with transmutation circles on his gloves, creating highly flammable conditions, and then produces a spark (from friction in the glove's cloth) to ignite it. This gives him precise control over flame direction, intensity, and range without requiring fuel.

What are his signature techniques?

• Basic flame attacks: Snapping fingers to ignite prepared air — seemingly effortless but requiring precise oxygen manipulation first.
• Ignition Cloth: His gloves are made of specially treated material that sparks when snapped.
• Targeting precision: He can direct flame accurately enough to cauterize wounds or destroy specific targets without harming surroundings.
• Mini-explosions vs. sustained burns: He adjusts both range and behavior of flame.

What is Mustang's weakness?

Rain. His alchemy requires manipulating air, and humid/rainy conditions make oxygen manipulation unreliable. He cannot effectively use his powers in rain — which is why the Lust fight (where he's forced to cauterize his own wounds repeatedly in rain) is so brutal, and why he eventually uses an alternative ignition source.

How strong is Mustang at full capability?

Extremely. In the fight against Envy and later against Pride and Gluttony, he operates at a level that overwhelms opponents who require multiple State Alchemists together. The Fuhrer acknowledges Mustang as one of the most dangerous soldiers in the military.

What does his alchemical specialty represent symbolically?

Fire purifies and destroys. Mustang uses the same power that burned Ishval to now try to fix what was broken. The alchemy doesn't change — his relationship to what he does with it does. That's the whole moral arc.