Lead is used mainly in lead‑acid batteries for vehicles and backup power, and in ammunition and fishing weights. It provides radiation shielding in medical and industrial X‑ray equipment and is used in cable sheathing, ballast/weights, roofing, and some solders and alloys. Historically it was common in pipes, paints and glazes, though many of these uses have been reduced for health reasons.

Lead can mean the heavy metal (chemical element Pb) — a toxic substance once common in paint, pipes, and petrol; exposure causes developmental, neurological, and cardiovascular harm, especially in children. It can also mean to guide or be in charge — to direct, influence, or occupy the foremost person or position in an activity, group, or situation.

Spelled "lead" can be pronounced two ways: "leed" when it’s a verb meaning to guide (e.g., "I lead the team"), and "led" (rhymes with "bed") when referring to the heavy metal or the past tense of the verb (e.g., "the pipe contains lead" or "she led the team yesterday"). The metal lead is toxic and requires precautions.

Lead is poisonous because it mimics and displaces essential metals, disrupting enzymes and cellular processes. It interferes with heme synthesis causing anemia, produces oxidative stress and mitochondrial dysfunction, and crosses the blood–brain barrier—damaging developing brains and causing cognitive, behavioral, and neurological problems. Lead accumulates in bone, impairs kidney and cardiovascular function, and harms reproductive health; no safe exposure level exists, especially for children.

Lead is a toxic metal that harms multiple systems. In children it impairs brain development, lowers IQ, and causes learning and behavioral problems. In adults it raises blood pressure, damages kidneys, impairs fertility, and causes anemia and neuropathy. High acute exposure can cause encephalopathy and seizures. Lead accumulates in bone and persists long-term, raising cardiovascular and cognitive risks.

The three types of lead are elemental (metallic) lead — the pure metal used in batteries, pipes and weights; inorganic lead compounds — salts and oxides found in old paint, dust and contaminated water/soil; and organic lead compounds — carbon-bound organolead chemicals (e.g., historical gasoline additives). All forms are toxic, especially to children and pregnant people, with different exposure routes and health effects.