Heavy metals, which have widespread environmental distribution and originate from natural and human activity sources, are common environmental pollutants. In recent decades, their pollution has amplified intensely because of nonstop discharge in sewage and untreated industrial wastes. Because they are non-degradable, they continue in the environment; therefore, they have received a great deal of care due to their possible health and environmental risks. Next contact of heavy metals, their metabolism and consequent excretion from the body depends on the existence of antioxidants (L-Arginine, Vitamin E, Zinc, etc.) associated with the reducing of free radicals by hanging the action of some enzymes. Hence, this book was inscribed to offer a deep understanding of the mechanisms involved in causing their toxicity in order to highlight the necessity for development of policies to decline contact to these metals, as well as to find substances that contribute significantly to overwhelmedtheir dangerous effects inside our bodies.