Southern Ocean phytoplankton inhabit an environment defined by chronic iron limitation alongside distinctive trace metal regimes, including relatively high zinc and copper and low manganese. While iron has long been considered the primary constraint on productivity in the region, increasing attention has turned to how other trace metals shape phytoplankton growth and physiology. I discuss results from laboratory culture experiments examining trace metal requirements and physiological responses across Southern Ocean phytoplankton. These include growth, photophysiology, and elemental quotas, providing evidence for metal substitution strategies, such as varied Zn/Co/Cd use in carbonic anhydrase and Cu/Fe substitution in photosynthetic electron transport. These results highlight that Southern Ocean phytoplankton are adapted to a multi-metal landscape, where co-limitation and substitution capacity can influence cellular function, community composition, and biogeochemical cycling.