Comment by hammock
“Silicon substrate, as one of the most important materials for the integrated circuit industry, can be used to manufacture mm-wave antennas for a highly integrated purpose”
Here’s an interesting paper on how to make it work efficiently:
https://www.mdpi.com/2079-9292/12/24/4983#:~:text=Silicon%20....
That neither makes silicon a metal, nor glass silicon (it's silicon oxide at best, and oxides generally have radically different chemical and electrical properties than the pure element).