I generally use foil to make embellishments or add some variety or texture to the piece. However you can also use it as the focal point, background and to stamp on. It is often embossed and then coloured with distress paints or alcohol inks. You can also die cut letters to create your own metallic text.
I have experimented with embossing my foil both before and after I have stuck it to card (it is self adhesive) and both work fine. It really depends what you plan to do with it afterwards, that is, if you want to maintain the self adhesive nature until after you have embossed and coloured then don't stick it to card!
Gears Texture Fade.
Use alcohol blending solution or an alcohol hand gel to clear your craft mat!
Once dry you can lightly sand the textured surface to reveal a bit of the metal.
I cut and embossed a piece of foil to fit inside the weathered clock.