New metalloprotein structures continue to provide discoveries regarding protein-metal ion partnerships. Many recent structures reveal metal ion sites that control or are controlled by protein conformational change, including modulation by alternative splice variants and striking conformational changes. Only a few novel catalytic metal centers have been revealed recently, such as the surprising Ni-hook superoxide dismutase catalytic site and the cubane-like Mn(3)CaO(4) photosynthetic oxygen-evolving center. However, important new variations on old heme themes, breakthroughs in the fields of metal ion regulation and metallochaperones, and captivating insights into partnerships between proteins and minerals have also been described. Very high resolution metal site structures and metalloprotein design will be increasingly important in order to leverage the wealth of native metalloprotein structures into a deep understanding of metal ion site specificity and activity.