In this chapter we introduce the concept of metabolism as a theoretical tool to understand the current relation between society and nature. The exchange of matter and energy between living systems and their ecological environment is an inescapable mechanism needed for the reproduction of the former. This applies to social systems, but at the same time this metabolic perspective allows us to perceive the concrete ways in which the contradictions of capital accumulation are generating ecological crises and catastrophes. Moreover, metabolism entails dynamics of local and global inequalities. As suggested by Bensaid (2002, p. 302), ‘the critique of political economy discovers a turbulent topology, divided up into basins, springs, wells, flows; an articulated space, imbricated and interlocking, whose fault-lines and fractures organize the metabolism of unequal exchange’.