There is much more to modern metallurgy than just the metal itself. It is often forgotten that slags and fluxes play an important role in the processes that we use to obtain the materials which are meanwhile an integral part of our technical society. Without slags there would be no copper production and no recycling of aluminium. Slags enable the metallurgist to treat complex raw materials, such as spent lithium ion batteries or electronic scrap. The understanding of their structure, composition and application is the key to establish new processes for these activities.An extensive scientific community has dedicated their research capacities towards the investigation of thermophysical properties of slags while others focus intensively on the processing, solidification and forming of the target metals and materials. However, for the design and optimisation of metallurgical processes it is very often necessary to have an equally close look at both phases and to focus on the interaction that happens directly at the metal-slag interface. During the past decade, various activities have been initiated at the Department of Electrometallurgy of Donetsk National Technical University and IME Process Metallurgy and Metal Recycling at RWTH Aachen University in order to understand metal-slag interaction in depth. This research ranges from basic interfacial phenomena to the design and application of new slag compositions for modern metallurgical processes with special regard to the thermochemical interaction of the slag with other present phases as well as the kinetics of the occurring reactions.Using the chemical reactions in metal-slag interaction as an analogy, two internationally renowned research teams were brought together in a workshop in Yalta with the goal to exchange ideas and findings, compare methodologies and gain a deeper understanding of the field of expertise across the boundaries of geographical distance and language.