Photography of murals and graffiti

https://peakd.com/hive-184784/@suezoe/engesp-wonderful-murals-and-graffiti-i-came-across-while-traveling-maravillosos-murales-y-grafitis-que-me-encontre-mientras-me

Hello! Idk if it's the right group, but I want to paint an electrical box in my neighborhood and have some questions.

I have worked on other surfaces before but not metal. Do I have to use something before I start painting? There is a tag I'll have to cover but I don't want the paint to start chipping away. Does anybody have recommendations what type of paint to use for (painted) metal surface? Any other tips? The surface area is huge and I'm a bit too broke for that much spray paint... I hope any of you can help, thanks!