The present invention relates to a plasma burner for metallurgical furnaces which is operated with gaseous mixtures, wherein an addition gas is fed to the plasma burner via a ring conduit into the inside of the burner. The gas conduction pipes on the addition-gas outlet are arranged at a predetermined angle to the longitudinal axis of the burner, 35.degree. to 45.degree.. The point of intersection between plasma arc and addition gas is 25 to 45 mm in front of the rod-shaped cathode. In order to increase the output with constant arc current and without chemical reaction with as molten material, hydrogen or nitrogen is used as addition gas; and when a chemical reaction is desired, oxygen or oxygen-containing gas mixtures are used.