1. Create a base image in what you want the final metallic color to be, background being transparent. For this tutorial I used a random shade of gray. This tut works on full sheets of alphas as well as a simple shape like a star, which is what I am doing here.
2. In the layers dialog box, right click and edit layer attributes, naming this layer "base".
3. Duplicate this layer (by selecting the double paper icon at the bottom) and name this layer "temp".
4. Layer Box > Base > Right Click, Alpha to Selection
5. Layer Box > Temp > Image Box > Select > Grow > 5
6. Now take a large brush in your selected base color and just wipe over all edges of your new image in the temp layer to fill in the empty spaces between the old image and the "marching ants". DO NOT deselect anything! [White used in tut just to show you where the new color was going.]
7. Layer Box > Base > Right Click, Alpha to Selection
8. Layer Box > Temp > Image Box > Edit > Clear
9. Image Box > Select > All
10. Temp Layer > Image Box > Filters > Blur> Gaussian >
Leave defaults, change number to 8
11. Layer Box > Base > Image Box > Filters > Map > Bump Map
Settings: Bump Map "temp" image, Compensate checked, numbers 135/45/8/0/0/0/0
12. Layer Box > Temp Layer > Trash Can
13. Base Image remains > Image Box > Layer > Colors > Curves
Settings for X,Y: 0,0 - 35,190 - 100,0 - 160,255 - 225,65 - 255,255
These settings are only approximate. If planning on reusing this tut then you can save these settings by clicking on the save icon and name.
14. Image Box > Filters > Noise > Scatter RGB > Settings all at defaults of .20 but you can change these to your liking. Deselect check boxes so noise is all the same color.
This part of your image is complete. If you wish to add a drop shadow I would stick to something subtle like settings of 2/2/4/60 although the curve and bump mapping does add enough dimension IMHO.