As @antibor says. You need metal to build electronics, and metal plus electronics to build advanced parts. As you research and build better ships with weapons you will find you need more electronics & advanced parts. You need mostly metal in the early game. But a bottleneck on either electronics or advanced parts will stymie your builds. If necessary, use the "civil acts management" dialog, "economic policies" section to temporarily boost one of the resources you are short of; but don't leave it unbalanced for long, you'll run out of whatever you haven't boosted!
Also, as he says, in this game there is no maintenance! That means that all your production is only useful for building new stuff, and after a while that mostly means new ships. That is why this game is all about building as much as you can, like an RTS.