(Steve Willner) writes:

In article ,
"John Zinni" writes:
When an astronomer/astrophysicist uses the word "metals" he/she is referring
to the group of all elements other than H and He.

That would be my first thought, but I might decide otherwise in some
particular context.

Sorry... can't help with the etymology. I'd expect it to be fairly
recent, though, because only in the 1930's was it realized that the
Universe is mostly hydrogen and helium.

Under sufficient pressure, some things you wouldn't think of as metals
apparently become metals. I think hydrogen is an example, but more recently
oxygen under pressure was shown to become a red metal and, under even more
pressure, became superconducting. I think the pressure was in the range
of 100 gigapascals. I read about it in Science News.
--
Ignorantly,
Allan Adler
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.