@Melonlity -- you can actually have the best of both worlds. If you just don't want to use a separate primer coat, there are a good number of paint products that also contain primer. That's right. You can have your cake and eat it, too.
This step is even simpler than using paint without primer because you won't have to use as many coats. One of the advantages of primer is that it helps keep the "old" color of the metal from bleeding through the new layer of paint. Those primer and paint combos eliminate that problem quite well.