I have drawn several designs to use for front and back covers for two books, one titled Flora, the other Birds & Bees.
I begin by taping the metal to a foam mat and then taping the drawing in place over the metal. I transfer my image to the metal by tracing over my pencil lines with an embossing tool. I remove the paper and use the embossing tool to deepen the lines on the metal and add details by working on the front and the back side of the metal, creating dimension. 
I like to make a small outline around my whole design and fill in the background with stippling by tapping the point of the tool repeatedly over the surface of the copper. This helps the main design stand out from the background.
I found the best product to color metal is Adirondack Alcohol Inks. You can apply inks using a felt pad or paint brush. I wanted to paint color in specific areas so I used a brush to apply the ink. You don't need much when working with the inks, just drop a few drops of ink onto a paint tray and use a paint brush to apply the ink to the metal. 
The ink goes on very bright. If you decide that you want less color, dip your brush in a little of the Alcohol Ink Blending Solution and go back over the area previously painted and the color becomes lighter as it removes the ink. Or you can add the blending solution to the ink on the tray and lighten it before painting it on the metal. The inks dry very quickly and can be reconstituted in the tray by adding a little blending solution. To rinse my brush between colors I dipped it in the alcohol blending solution and wiped it on a paper towel.
On the copper design with the waterlilies I lightened the ink to make a soft pastel tint on the copper and I painted the ornate floral design brightly to look more like the metal ornaments you see in Mexico.
