Industries often release untreated effluents into the environment resulting in elevated levels of toxic pollutants such as heavy metals in groundwater and drinking water sources which contribute significantly in environmental pollution. Lead and arsenic are among the major contaminants that pollute water systems. Prolonged exposure to lead and arsenic in water can result in adverse health effects such as skin lesions, discoloration, extremity spotting, increased risk of skin cancer, and damage to the lungs and kidneys. Various methods have been used to remove arsenic and lead contamination, but bioremediation using biomass from bacteria, algae, fungi, and yeasts has gained considerable attention from researchers as a promising approach in recent decades. This book chapter discusses the microbial bioremediation of heavy metals particularly lead and arsenic through various mechanisms including efflux, biosorption, exopolysaccharide secretion, bioaccumulation, biotransformation via oxidation/reduction pathways, bioleaching, oxidative stress, and biomineralization. Additionally, the chapter analyzes information on the bioremediation of different metal ions by metal-resistant bacteria.