Materials that can be etched

Natural materials
Directly "burning" images on wood were some of the first uses of etch lasers. The laser power required here is often less than 10 watts depending on the laser being used as most are different.Paper masking tape is sometimes used as a pre-etch overcoat on finished and resiny woods so that cleanup is a matter of picking the tape off and out of the unetchd areas, which is easier than removing the sticky and smoky surround "halos" (and requires no varnish-removing chemicals).
Plastics
Standard cast acrylic plastic, acrylic plastic sheet, and other cast resins generally laser very well. A commonly etchd award is a cast acrylic shape designed to be lasered from the back side. Often the laser etch is followed by paint filling the etchd surface to produce more contrast between the etchd surface and the surrounding surface.
Metals
Laser on Stainless Steel (SS316L)
The best traditional etch materials started out to be the worst laser-engravable materials. This problem has now been solved using lasers at shorter wavelengths than the traditional 10,640 nm wavelength CO2 laser.
Coated metals
However, the same conduction that works against the spot vaporization of metal is an asset if the objective is to vaporize some other coating away from the metal. laser etch metal plates are manufactured with a finely-polished metal, coated with an enamel paint made to be "burned off".
Stone and glass
Stone and glass do not turn gaseous very easily. As expected, this makes them generally a better candidate for other means of etch, most notably sandblasting or cutting using diamonds and water.