Heavy metal and Metallic element

Heavy metal noun - A metal of relatively high density (specific gravity greater than about 5) or of high relative atomic weight (especially one that is poisonous like mercury or lead).

Metallic element and heavy metal are semantically related. In some cases you can use "Metallic element" instead a noun phrase "Heavy metal".

Metallic element noun - Any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc..

Heavy metal and metallic element are semantically related. Sometimes you can replace phrase "Heavy metal" with "Metallic element", this phrases are similar.