Why is iron so important? A major function of iron is the creation of both the hemoglobin protein, responsible for carrying oxygen to the body, and the myoglobin protein, responsible for storing oxygen in the muscles. When infants, children and teenagers grow and mature, they need iron in order for the process to occur properly. Iron is a component of many enzymes in the body and is also key in the development of the brain, vital in the first 2 years of life.