Metal elements are indispensable for maintaining biological functions in a living body. These metal elements change their chemical nature depending on their redox states and act as not only essential elements but can become harmful cofactors inducing disease depending on the conditions in the living environment. Examination of the molecular mechanisms relating to metal elements by physicochemical approaches is crucial for understanding structural and functional roles of the metal elements. From this viewpoint, our laboratory researches the interactions of metal elements with various environmental molecules including dietary fibers, plant pigments, protein complexes, and toxic pollutants, by using spectroscopy, calorimetric analysis, and theoretical calculations.