In materials science, “plastic” refers to the ability of a material to undergo permanent deformation under stress without breaking. Metals exhibit plasticity when they are subjected to stress beyond their elastic limit, allowing them to be shaped or formed. This property is distinct from the common use of the word “plastic” to describe synthetic polymers.
Metal is also elastic.
But that doesn’t mean metal is plastic or elastic in terms of material type, just the English sucks.
Yeah words have special meanings in special regimes. There are a lot of regimes these days, with so much known about so many specialities. We could spend all day noting use of words that make sense within a particular science or engineering field but would be funny in casual conversation .