When engineers drilling geothermal boreholes in Iceland’s volcanically active Krafla region in 2009 unexpectedly struck a magma body some two kilometres down it opened up the possibility both of studying magma in situ and of using heat from magma directly as an energy source. Recognizing the novelty of this event, I explore some of the ways that magma might become politicized over the coming years—using a conceptual framework that involves three distinct, though related, approaches to the political geology of magma. The first, drawing on political ecology, looks at how power from magma fits into Iceland’s recent energy-intensive, capital-attracting development strategy. The second, taking insights from relational materialist thought, considers how the specific properties of magma might trigger new political mobilizations. The third, more speculative and philosophical in tone, reflects on how we might see magma and other geological forces as the very condition of possibility of the political—as forms of ‘geopower’ that antecede, subtend and energise all social and political formations. Taken together, these three approaches suggest an open, experimental approach to the formation of new political issues and subjects in which new kinds of ‘becoming with magma’ defy prediction.