Even though handguns dont matter ...
Kahr K, MK and T series and Rohrbaugh are a couple off the top of my head.
As for rifles, there are no 100% metal guns (if you count parts like grips, stocks, mags and other accessories).
But there's several HK rifles (G3s, MP5s, PSG-1) Sig 550 (and variants), FN M249 SAW, Barrett .50BMG rifles, French FAMAS, British SA-80, and I'd still consider the M4 a modern rifle.