Metals have played an important role in medicine for years,ever since humans have walked the planet. Many are essential in our diets in varying quantities, although people have recently realized their significance.Metal ions bond with ligands in some process, to oxidize and reduce in biological systems.The important metal present in the body is iron which plays a central role in all living cells.Generally iron complexes are used in the transport of oxygen in the blood and tissues. An adult at rest consumes 250ml of pure oxygen per minute, this oxygen carried by the metal complex transport system known as heme, allowing the oxygen to leave the blood when it reaches the tissue. The heme group is metal complex, with iron as central metal atom, which bind or release molecular oxygen.