Caroline's Truck:
It depends on what the surface you apply it to is made of. If it's non-ferrous, then absolutely. If it's not rusty ferrous metal, then yes. If you've got some rust, then go for it.
They recommend that you power wash any grease off the surfaces with the degreaser agent before using metal ready.
Hot Rod Dad:
It seems that you need to prep a non-rusty surface, and anything that you want to paint that's non-ferrous metal. If you have a rusty surface, make sure you knock off all of the loose rust (the stuff that falls in your eyes when you're screwing around underneath the truck) and any large scales. You shouldn't have any problems.
