Ammonia and optionally carbon monoxide are injected into the flue gas containing metals such as mercury in a manner so that there are sufficient amounts of these materials in the flue gas when the flue gas is at a temperature of from 900.degree. F. to 1,450.degree. F. to oxidize the metals within the flue gas. The oxidized metals are then attracted to particulates present in the flue gas. Oxidation is facilitated by a reaction zone stabilizer through which the flue gas flows. The stabilizer provides a stable continuous ignition front. These particulates bound with oxidized metals are removed from the flue gas by a particulate removal device such as an electrostatic precipitator or baghouse. After the ammonia is injected, the flue gas can be rapidly cooled to a temperature below 500.degree. F. to minimize decomposition of oxidized metals in the flue gas.