The metal used in batteries and is highly toxic is lead. Lead has been widely used in lead-acid batteries, commonly found in vehicles and stationary power supplies due to its ability to efficiently store and supply energy. However, lead is highly toxic, particularly to humans and animals, as it can cause serious health issues, including neurological damage and developmental delays in children. Concerns about lead exposure have led to regulations and bans on its use in many applications, advocating for safer alternatives in battery technology, such as lithium-ion batteries, which are less harmful to human health and the environment.