Alkaline metal and Metallic element

Alkaline metal noun - Any of the monovalent metals of group I of the periodic table (lithium or sodium or potassium or rubidium or cesium or francium).

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

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