I'm new to blender (and 3D modelling) so please use dummy terms if you answer!
I have applied 3 materials one each to 3 different objects and only 1 renders the same as the material preview. I've attached a screenshot to show you what I mean. The silver material should be on the top ball and the brass material should be on the cylinder holding the ball up. I've no idea why it's not working when the copper material on the spiral wire worked. I'm using cycles render if that helps?