Yes, I use .024 with gas for body panels and where it is really useful is welding exhaust tubing so you do not burn thrrough the thin metal or totally distort the flange you are welding on to the pipe.

Solid core is much cheaper in the long run over flux if you do a lot of welding.

You can do sheet metal with flux, it is just messier in general, especially the splatter and clean up. For working on the interior of the car, the solid core is much better.

I go here for expert welding advice:

http://www.hobartwelders.com/