Lead is a ductile, very soft, highly malleable, bluish-white metal, which has been used by mankind for over 7,000 years. Of the common metals, lead is the second-densest (and therefore second-heaviest by volume), second only to gold, a connection not lost to medieval alchemists.
The Latin word for lead is plumbum and hence its atomic symbol is Pb. It is from the use of lead for pipes that we get the word plumbing.
Lead is too soft to be used as a cutting edge and, in addition, too heavy to be used as armour. However, it does not rust when exposed to water (only when exposed to certain acids), and is therefore highly useful in a variety of roles. Lead sheeting was often used to roof buildings, for instance. The Romans used lead oxide as a sweetener in wine.
Firearm projectiles (whether bullet or ball) have traditionally been made of lead for maximum weight and stopping power. Even modern firearms use lead bullets (typically copper- or nickel-jacketed for added efficiency).
Unfortunately lead is poisonous. Long-term lead poisoning leads to a variety of symptoms including reduced mental capacity, anemia, bipolar behaviour, gastrointestinal distress, and the formation of a tell-tale bluish line along the gums (called a Burtons's Line). In extreme cases, lead poisoning causes seizures and death. Children are particularly susceptible to lead poisoning. For this reason, lead is not commonly used in the modern world (excepting bullets), although chemical compounds containing lead are sometimes used.