A metal is also, in astronomy and astrophysics, a term for any element that is not hydrogen or helium. Since the universe is still made up of around 99% of these two elements, anything heavier is grouped together by astrophysicists as "Metals". Even the small amount of metals found in a star can greatly change the dynamics of its evolution.
Also, very little of what is called "metals" are actually what a chemist, or even a layman, would call a metal. The transition metals like chromium, titanium and iron form only late in the development of a star, while heavier metals, such as Gold, Lead or Mercury, need a supernova to form. Most of the metals in a star are Carbon, Nitrogen, Oxygen, Neon and Silicon, with a smattering of other elements. I am sure that most chemists would shake their heads at Neon being called a metal, but nomenclature often does not make sense.