In addition to environmental and climate policy objectives, the Circular Economy is also essential for strengthening the security of supply and for achieving further economic and socio-economic goals. Recycling is one of the key factors along with a range of other approaches and strategies (e.g., longevity, Intensity of use, and the sharing economy). In order to assess the contribution and the limits of recycling for sustainable resource use and climate protection, there is a need for a clear definition of the assessment framework and system boundaries, as well as for precisely formulated calculation approaches and indicators. In this paper, the Resource Commission at the German Environment Agency (KRU) summarizes the current state of knowledge on recycling and recommends possible indicators with a focus on metals, which play a key role in the energy transition and for climate protection.