What very dense malleable metal is used for plumbing solder bullets and shields against radiation?

The very dense malleable metal used for Plumbing solder, bullets, and radiation shielding is lead. Its high density makes it effective at blocking various forms of radiation, while its malleability allows it to be easily shaped and formed for various applications. However, due to health concerns associated with lead exposure, its use in certain applications has been restricted or regulated in many regions.