Hi Kristian,
Cutting steel is not easy on a scroll saw. It all depends on how thick it is. Most would use a diamond blade, they are very expensive. If the metal is very thin the metal cutting blade would be OK.
For fiberglas, I would use a blade with no reverse teeth, like the Polar blade. A # 5 is used the most.
Check out my web site.
I worked two years in Sweden, Stallarholmen and Stora Tun each 1 year. Had a great time.
FD Mike