Renewable technologies are seen as a possible path for a sustainable energy system. On the other hand a variety of metals is needed for both the production and the operation of renewable technologies, which are not available in infinite amounts. This work discusses the importance of rare metals for renewable energy and sustainable technologies. This theme is discussed based on research for thin-film photovoltaic (PV) systems working with Indium and Tellurium and batteries for electrical vehicles working with Lithium. Based on existing literature the specific metal demand for the technologies and the available amounts of resources are discussed. For both values very different numbers could be found. The specific metal demand is between 22-109 g Indium per kW PV module, 31-279 g Tellurium per kW PV module and 100-423 g Lithium per kWh battery storage. In five business scenarios (three for PV and two for electrical vehicles) the future demand for the metals is calculated and compared to the available resources. The material demand in the year 2050 among the scenarios varies between 4,518-31,130 t Indium, 9,486-65,352 t Tellurium and 20-27 Million t Lithium. The results show, that optimistic scenarios regarding the usage of PV and electrical vehicles might lead to significant shortage of the needed metals. However due to improvements in production efficiency or because of the discovery of new depots the picture might change in the course of time. Recycling technologies are discussed as one strategy as well as the impact of certain recycling rates.