NOTE: I'll be assuming, that you know how to some features of Photoshop like levels, layers and selections.

That metal look. Quite 'pop' these days, isn't it? Too bad, then, that it is often not done right.
People forget the basic properties of metal: shinyness and reflectivity.
So, let's create a few metal spheres.

First, create a new image, say 500x500 in size.

Then, make a spherical selection with the elliptical marquee tool. (To make sure it's a perfect sphere, hold down the shift key, while dragging.)
To get an easy 3d ball, let's use the radial gradient tool.

Create a new layer, and set your foreground color to white, and your background color to black, and decide, where the highlight of the sphere is going to be.
Drag from this point to the furthest point on the edge of the sphere, to create a gradient like this:

Then, use levels to enhance the highlight like this:

Let's add some scratches. Use the burn and dodge tools to do this (smallest brush), and keep in mind, that the scratches should curve around the highlight.

Now, let's add an 'environment map', something for the sphere to reflect. Create a new layer on top of the sphere layer, and use the clouds filter on it.
select the transparency of the sphere layer, and ause polar coordinates and spherize (strenght 100) on the clouds layer. Invert the selection and use clear.
Set the clouds layer to overlay, and the opacity to about 60-70 %. It should look like this:

Let's not stop here, though. Let's create another, smaller sphere(in it's own layer, of course.). Do the same things you did for the first sphere.
(I was lazy, and just copied and resized the first one.)

Now, obviously, these need to reflect each other. So, let's add that effect. Make a copy of the layer with the smaller sphere in it (let's call this layer sreflect) and place it underneat the original layer, and move it towards the center of the larger sphere a little. (You have to experiment to see how much this is.) Then, select the transparency of the larger sphere layer, and use the spherize filter on the sreflect layer. If the effect isn't right, use the filter again. invert the selection and clear. Set the sreflect layer to overlay (You may have to use different blending modes depending on where the smaller sphere is situated). I noticed the effect wasn't strong enough, so I made a copy of the sreflect layer to sort of 'double' the effect. Add a drop shadow in a new layer , and do the same spherizing thing as above. (use Eye candys drop shadow if you have it and remember to use the draw everywhere option, or select the transparency of the layer with the smaller sphere, feather the selection, move it a bit and fill with black.) Here it is:

Now use the same technique for the reflection on the small sphere.
This is the end result:

This is a VERY simple version of what you can do with this. Experiment a little, and spend some time on it, you'll get much better results.