Gas meters will be painted at the gas-meter factory. When factories (with an institutional customer) paint things in production, they use the very best paints, which would be a 2-part LPU over 2-part epoxy primer. Or lately, powdercoating with chemicals of similar quality. (they jack the cure temperature to 400F, so they can sell it to you pre-mixed in one can, but you must oven cure it.)
You can't touch that kind of durability with any consumer-available paints.
Such paints have a very tough outer sheen that won't take paint. If you want to repaint it because you don't like the color, you would need to scuff up the paint, e.g. with a Scotchbrite pad.