Metals which have high molecular weight and density higher than water are called heavy metals occurs naturally in earth crust. They are widely distributed in environment due to their multiple applications in agriculture, industry and medicines. According to some literature these metals are also called trace metals because of presence in minute amount in environment ranges to less than 10ppm.There are many factors like temperature, sequestration, adsorption and phase association which influence the bioavailability of metals. Metals are different types such as molybdenum (Mo), nickel (Ni), selenium (Se) and zinc (Zn) and lead (Pb) etc. which have different physiological and biochemical functions.These micronutrients show deficiency syndromes due to inadequate supply (1).