Aluminum or anodized aluminum?

You won’t see anything on non-anodized aluminum, the laser can’t really engrave the metal.

If you engrave silver anodized aluminum, your contrast will be very low. You’re better off getting a colored anodization, black, red, etc. The laser blows the color away and you get silver engraves on the color background.

The or for sourcing.

Search the forum for “anodized engraving” and you’ll find a lot of posts showing you what you can expect.

Here’s one I did.