Heavy metal (HM) pollution is one of the major concerns rising nowadays due to its toxic, accumulative, and persistent nature in the environment. Accumulation of such contaminants in the environment could negatively influence different biotic and abiotic components of the ecosystem. This chapter provides a comprehensive analysis of different HMs generated through natural or anthropogenic sources and that pose a severe threat to the environment and different ecosystems. Also, it will give detailed information on the potential ecological risks associated with different ecosystems when exposed to these HM pollutants. How physiological functions of single species are affected by these toxic HMs and ultimately affect demography of the population at the community level of that ecosystem is also discussed. The pollution status of different HMs distributed in different ecosystems, their uptake into biological systems, and their translocation through the food chain will give an outlook on the potential ecological risk associated with different HMs. The consequences of HM contamination to different ecosystems, evidence of their impact by placing particular emphasis on bioavailability, uptake, bioaccumulation, biomagnification, and tropic transfer are also reviewed here.