Without the proper laser is may be impossible to etch directly on the metal without ruining the laser, but fortunately for us there is Powdercoating.
If your looking for the quick info on this tutorial then it is 75,70,1000 and I'll get into why below.
First look at the metal you are going to powder coat and then the color you wish to apply. If the metal such as this steal is dark, then a darker color will make it less visible after being etched. Additionally, I recommended a 3 step process unless you are using aluminum. Powder-coat, Laser Engrave, and Powder coat with a clear coat to protect from rust.
So first Powder coat the color you want.
Next, Jump on a laser and put in your design. Powder-coating doesn't seem to carry over a gradient so try and make a design 2 colors, black and white, like a stencil, otherwise you may get mixed results.
With the settings 75 Power, 70 Speed, and 1000Hz in your favor, the laser will pass through up to 2 coats of powder. This is where is gets interesting, if you apply a three coats of powder before etching at 75,70,1000 your first coat will become visible again and there will not be a need for anti-rust protective clear coating. You could also try and just remove the first layer with 45,70,1000, but make sure you do a test first as powder coating thickness can be an exact science.
Thus far, the only complications that could arise is not having a good ground when powder coating multiple coats, keep a small file near by and remove some so that the metal is exposed for your hook.
Hope that helps.