In a method for sealing a tap opening in a metallurgical container a plug with a plug sleeve and a refractory flowable material is provided having a metal rod or pipe surrounded by a protective pipe connected thereto. The plug sleeve and the protective pipe are made of a material resistant to a molten mass of metal in the metallurgical container only for a short period of time. The material is a temporarily heat-insulating material which cokes within the molten mass of metal and is cardboard or wood. The time of introduction of the plug sleeve is controlled based on measured parameters of the molten mass. The plug is introduced into the tap opening by guiding the plug with the metal rod or pipe through the molten mass in the metallurgical container. The plug sleeve changes by temperature action of the molten mass of metal such that the flowable material is distributed in the tap opening and seals the tap opening. The tap opening is then closed from the exterior of the metallurgical container and the plug sleeve in the tap opening as well as the protective pipe are coked and destroyed.