Welcome to the Bunnings Workshop community @joebugeja. It's sensational that you've joined us, and many thanks for your question about non-slip paints.
Could we please trouble you for a few more details on your project? It would be really helpful for our members when offering assistance if they knew what type of metal it is, whether this metal is on the ground and if there is any corrosion or rust on it currently. Some images would really paint the picture for us.
If you can fill in those details for us, I trust you'll receive plenty of helpful advice.
We'll be looking forward to hearing more about your project.
If this is for a heavily trafficked area, I suspect you'll need a relatively hard-wearing industrial coating. Is this to comply with safety regulations?
All our non-slip paints are for paved or concreted surfaces. We have the Dy-Mark TreadRite - 1L coating, which can be applied over primed metal. It isn't paint, though, so you don't have any colour selections available, and it's also only really designed for foot traffic.
Do you already have these road plates, as I've heard of specific non-slip plates being manufactured? If you already have them, have you considered covering the plates with something similar to Croc Grip 100mm x 8m Black Anti Slip Tape? It has an aggressive 60-grit surface.
Please let me know if you have any questions.