This chapter focuses on lead, mercury, cadmium, selenium, chromium, manganese, and arsenic, and examines their effects on birds, as well as explaining the rationale for the elements. Metals have been responsible for some large-scale avian mortality events. These include mercury poisoning of seed-eating birds and their predators from mercurial fungicide-treated grain, lead poisoning of waterfowl and vultures from ingested shot, and selenium poisoning of waterbirds from agricultural wastewater. All forms of mercury are toxic to all forms of life. There is no evidence that mercury is an essential trace element for any organism. Methylmercury is taken up by bacteria and phytoplankton at the bottom of the aquatic food chain. These are consumed by zooplankton, which in turn are consumed by larval fish, small fish, larger fish, and eventually by predatory fish, birds, or humans.