Within the metallurgical industry as well as the underground mine industry, there is a need for on-line level detection in the different production processes and their material feeding systems. Microwave technology is a versatile, non-invasive measurement technique, which has a number of advantages compared with penetrating probes, laser and radar technology, and echo sound technique. In its extension, it could also be used for qualitative and quantitative analysis of waste gases due to the presence of specific molecules. This contribution describes the introduction of microwave technology in different metallurgical as well as underground mine production processes with the emphasis on EAF's.