Metals reflect most of the light from a CO2 laser, and act as very good heat conductors. With a 130 to 150 w CO2 and oxygen assist it is possible to cut thin metal, but it is slow, relatively dangerous (oxygen!), and usually uses a special metal cutting head.
Cutting with 60W isn’t possible. But you can ‘mark’, using various methods including etching off painted coatings, bonding a coating, such as Cermark or molybdenum disulphide (moly spray), bonding paint, bleaching anodised coatings, etc.
Even at higher wattages, laser cutting and ablation require specialised machines, capable of handling the extreme heat of molten metal as well as the fumes produced.
A high-wattage machine not designed for metal can easily crack lenses, coat mirrors and lenses and other parts with metal vapour.
There are cheaper options, one being fibre lasers with galvanometric heads. They can’t cut, but can natively engrave metal. And compound lenses can get the light pressure high enough to ablate metal, but at some cost in lenses and lens tube and there’s still the problem with excessive heat - reasonably easily overcome.
Careful settings and proper paint curing times can achieve the same effect, by ablating the top coat, but it’s a lot easier to just spray over anodised sheet.
ACP (aluminium composite panel) is great for solid objects. It comes anodised in a wide range of colours, can be machined with normal woodworking tools, and is stable outdoors for ~20 years. I buy mine from sign supply stores, or just go to a local sign shop for a small quantity or for offcuts (sold cheaply - they throw away a lot of smaller pieces, perfect for laser engraving).
@Bonjour is correct. It won’t damage your machine.
I know it sounds crazy but I saw a FB post yesterday where someone with a 50W CO2 (10mm/s 60power 0.01mm fill) actually engraved (with some depth) on stainless steel by using a layer of ketchup on the metal to be engraved. It has something to do with the acidity. It was crazy, they tried mustard, ketchup, and some other condiments but ketchup worked the best. https://www.facebook.com/groups/LaserEngravingAndCuttingGlobal/permalink/2695238424119659