All of the lead in the universe came originally from inside stars.
Because lead has so much mass, people use it for weights and for bullets. The large mass gives it a lot of momentum. Lead is also very soft and doesn't corrode (rust) very much, so people use it for building, for instance to seal joints in roofs so the water doesn't get in.
To find out more about atoms, check out these books from Amazon.com or from your library: