I've been making some coils with wires and I find out that sometimes they work and sometimes they don't work at all, the inside of those that don't work are some what more "silver-ish", more "metal-ish" like iron. While the coils that do work do look more thin like copper. Does the conductive material used for the coil matter? (If it does I'm -greatly- interested in why)
The core is very important in making a successful inductor, as a good core massively increases permeability (the ability for magnetic currents to flow effectively in the core - a lot like inverse electrical resistance (conductance.)) However, adding a core introduces a saturation characteristic; if the current approaches or exceeds the saturation point, the core will loose permeability and the inductor behaves more like a piece of wire.
The actual wire is less important. Generally low resistance and high temperature resistance are desirable factors. Copper is good.
Definitely the conductive material itself will matter - different materials will have different resistance and so for the electrically equivalent circuits you will need different wire cross-sections and that will significantly affect winding size.
Now to "silverish" vs "copperish". The deal is you need the winding turns being insulated from each other, otherwise the winding just gets shorted.
"Copperish" wires have their looks because they are either coated in enamel (lacquer) or covered with copper oxide and both are insulating materials (however you need to check whether their insulating properties are actually enough for the specific application).
"Silverish" wires don't happen to have insulating coating and so when winding turns touch each other the winding gets shorted. The solution could be to leave gaps between turns and then cover the winding with lacquer so that turns don't move. Again, different layers of winding should be separated by an insulator and you have to check whether the lacquer and the insulator and the distance will suit the actual application.