This article discusses the politics of direct action against fossil fuels put forward by climate justice movements, focusing in particular on the tactic of the blockade. Drawing on the conceptual toolkit of urban political ecology, the argument moves from a critique of the consensual regime of climate change governance to highlight conflict and dissent as central forces for the transformation of the socioecological metabolisms structuring the capitalist urbanization of nature—of which fossil fuels constitute the lifeblood. This approach shifts the debate around climate change politics from an issue of technological transition to one of metabolic transformation. On this basis, the article proposes a characterization of direct action against fossil fuels as expressions of metabolic activism: instances of grassroots ecopolitical engagement that aim to break consensus by disrupting capitalist-driven metabolic relations while also experimenting with alternative values, knowledges, spaces, and sociomaterial relations. To ground these reflections, the article offers an account of the Swedish climate justice coalition Fossilgasfällan and its successful three-year campaign, culminating in a blockade to halt the expansion of the gas terminal of Gothenburg port.