Despite the availability of a vast variety of metal ions in the periodic table, biology uses only a selective few metal ions. Most of the redox-active metals used belong to the first row of transition metals in the periodic table and include Fe, Co, Ni, Mn, and Cu. On the other hand, Ca, Zn, and Mg are the most commonly used redox inactive metals in biology. In this chapter, we discuss periodic table’s impact on bioinorganic chemistry, by exploring reasons behind this selective choice of metals in biology. A special focus is placed on the chemical and functional reasons why one metal ion is preferred over another one. We discuss the implications of metal choice in various biological processes including catalysis, electron transfer, redox sensing, and signaling. We find that bioavailability of metal ions along with their redox potentials, coordination flexibility, valency, and ligand affinity determines the specificity of metals for biological processes. Understanding the implications underlying the selective choice of metals from the periodic table in these biological processes can help design more efficient catalysts, more precise biosen-sors, and more effective drugs.