Not enough info about it. Stainless steel, magnetic iron, and carbon fiber may be good for building parts for wind generators, steam engines, and much much more, or maybe not, not enough info about it to tell much yet.

How do each hold up to outdoor use in the elements? Heat? UV from the sun? Etc...

PLA I hear a bit about being bio degradable. How does that effect Stainless steel, magnetic iron, and carbon fiber filament? Will a part last forever or degrade in 5-10 years?

How well does magnetic iron conduct? Is it like a real steel, or like tin plated rubber in use?

All of those filaments may have many great uses, but not enough info to know.

Carbon Fiber for instance may work great for small wind generator blades and or hubs, strong and solid? Or would it just snap to pieces in high winds and storms?