Well, welcome to the forum, I hope you find the information you're looking for in here. I see that you are interested in a laser in the BST section. Good luck in finding that special laser that everybody wants. There are a lot of good deals going on at the moment.
Metal etching generally uses a removable coating that is designed to absorb a specific laser wavelength and convert it in to heat to be delivered to the metal substrate to be etched. Metals tend to reflect laser beams and not absorb them. You can overcome the reflectance with a high enough intensity, but you are looking in to multi-kilowatt CO2 systems for CW or q-switched multi-joule systems for pulsed applications. Neither tend to be hobbyist friendly. You can etch thin metal with a properly focused 15W CO2 laser and the right coating.