We commonly find lead shotgun pellets under the skin of field dogs, usually when taking X-rays for some other reason. This type of lead exposure is not associated with significant toxicity, the lead must be ingested for problems to occur. The other common metal poisoning in dogs is zinc. Zinc toxicity causes a severe hemolytic anemia. Red blood cells are broken down rapidly within the body, and anemia results.
Kidney failure can result from zinc toxicity, and is a life-threatening complication.
Zinc is present in many different items. Commonly ingested are zinc containing skin ointments, plumbing nuts, and game pieces from board games such as Monopoly. The most common source of zinc poisoning in my experience is pennies minted after 1982. These coins have a high zinc content, and result in severe illness. Zinc poisoning can be fatal, and severe illness develops quickly.