You can use one of several methods. Let's say you want the
shape of each letter to be "cut out of copper" you use Mask Generator
Luminance Mask.
Place text on topmost track, followed underneath by copper metal
(such as from cgtextures.com). Make the copper track a child.
Set the FX on the text track and change the compositing mode
to Multiply (Mask).
Your video is below everything on the third track.
Another method is to use a greyscale of the textures and bump map.
This would be more like a rough surface like stone.
YOu can use a combination where the letters look worn or corroded away.