Admittedly, it might be possible if you had a silicon-based lifeform, but silicon is viewed as much less flexible and stable than carbon, since it can't form double and triple bonds even though silicon has four valence electrons.
Now, a hybridized carbon-silicon lifeform might show some promise for metallic or pseudometallic body structures, but they wouldn't exist at high temperatures. In addition, you need to develop an entirely different metabolism, including silicon-based organic compounds.
Another issue is water, in which silicon dioxide dissolves. You'd need a different universal solvent, which would be very difficult to find. So it's reasonable to conclude that metallic or pseudo-metallic structures on the organ level are impossible, at least with our current knowledge of organic chemistry. Here in NESlife, it's assumed that organisms follow the carbon cycle for their metabolic reactions.
