The transition to a renewable energy platform for the generation, transmission, and storage of electricity, requires a sufficient supply of key metals, in particular the so-called “battery metals” tin, lithium, tungsten, and tantalum. These metals are primarily sourced from magmatic-hydrothermal deposits, which form when mineralising fluids exsolve from evolved, volatile-saturated magmas. Here, we show how geochemical microanalysis of accessory minerals can help shed light on the processes of crustal melting and of fractional crystallisation, which together lead to mineralization, and how such a bottom-up approach may help us build better models for the formation of these deposits. We also discuss how in a global mining context these battery metals are relatively small-scale, with a fragile supply pipeline, and by taking the example of tin in the 2000’s discuss the current rush for lithium.