There is a similar tutorial, for creating gold objects, by Rob A, found here. This tutorial is the "Text" spin-off, from Rob's tutorial.
Environment Image used:
Open any size image with a white background. My image is 800 x 400 px.
Select the Text tool and use any font of your liking. I am using Apple Garamond Bold, using black and size at 250. Center the text on your image using the Alignment tool.
Reselect the Text tool, select the existing text and click "Path from Text".
Right click the text layer and choose "Layer to image size". Right click the text layer again and choose "Flatten image".
Duplicate the flattened layer.
On the new duplicate layer, go to Colors - Invert.
Add a Gaussian blur of 12 px to the duplicate layer.
Turn off the duplicate inverted layer (click eye).
Select the bottom layer. Right click, "New Layer". Select white.
You should now have a blank white layer between the top and bottom layers.
Open the Environment image in GIMP (shown at the top of this tutorial). (You can also save this as a pattern in GIMP by saving it to your username/.gimp-2.6/patterns folder).
Go to Filters - Light and Shadow - Lighting Effects.
Choose the Environment tab, check Enable Environment Mapping and select the image you just opened from the list.
On the Bump Mapping tab, check Enable Bump Mapping, select the inverted text layer (top most), Linear, and .02 for Maximum Height.
On the Options tab, check the Transparent Background and High Quality Preview, then select OK.
In the Path Dialog, activate the text path selection.
Go to Select - Invert. Press the "Delete" key to remove the excess.
You can use the Move tool to move the blurred layer out a bit (I use the arrow keys after selecting the Move tool and selecting the layer.) If you move the blurred layer out and transparent areas show up around the image, simply add a new white layer to the very bottom of your Layer dialog.
To change the metallic look of your text change your Environment image when running Filters - Light and Shadow - Lighting Effects.
Here are 3 additional Environment images you can use:
NOTE: You can use or create any pattern you wish, to use for an evironment map, other than the ones presented here in the tutorial.
You're done! Enjoy! :)