Not without chemical coating. It can etch anodized or painted surfaces, and you can bind cermark to metals. To actually engrave metal you need something a bit different than a CO2 laser.
Depends on how curved the surface is. I'd think a set of grips would be ok. There is a finite focal length on the lens before it starts getting out of focus.
[video=youtube;o4ccNRMTpGQ]https://www.youtube.com/watch?v=o4ccNRMTpGQ[/video]