Heavy metals is a vague term for a group of metallic chemical elements that under some definitions can refer to the vast majority of the metals known to science. In biological/medical terms heavy metals are a much smaller group, that for many practitioners is restricted to those that are potentially toxic. Of course, several of these metals are beneficial - indeed essential - for normal physiological function. However when they enter the body in large amounts or in different forms they may be poisonous.
Toxic heavy metals may include: