I hate to say this but you will need to at least mention the printing process that will be used.
For short runs, sometimes it can be printed in CMYK and for long runs it's another process similar to screen printing.
In the first case, you can refer to this question. The kind of black you'll choose will depend a lot on what's around it and the size of the white text you mentioned. Plus, you might want to use a "light" recipe for your rich black since metal isn't very porous (e.g. don't use a lot of CMY in your recipe). In your case, you'll probably want a black that doesn't have more magenta than everything else; only you can judge what tint your black should have to make your design look great and it's not true there's a "one black fits all". Some printers also have their favorite recipe but that doesn't stop you from using your own, as long the total of ink is within the print requirements of your printer (in general, it's maximum 300 density when adding the CMYK values together).
And if you need to print using a limited amount of inks, you'll probably simply select a nice Pantone black and use it as a separation color with your other Pantones. Sometimes you need to add a white background as a base to make sure your design won't appear semi-transparent once printed. If you work with Photoshop, here's an example and another one that can help you get started on how you'll need to use channels to create your file. With vectors that's easier, you'll simply need to make sure your colors are spot colors.
The rules to follow are usually the same as with any other Spot printing; you need to make sure you use the same spot names everywhere in your swatches and verify your color separations to be certain no element is left in CMYK, otherwise they won't be printed. You can use different type of trapping sometimes (e.g. overprint) to create new colors by mixing your Pantones but for that too, it's something you should ask about to your printer first. It's possible you won't be able to use any transparency or tint; only 100% densities for your Pantones. That's another thing you'll know by asking what's the print process and checking the printer's requirements.
Finally, it's also possible a transparent vinyl will be used and usually the technique is the same as the second one mentioned above.
But before you truly get started, the wise and smart thing to do is to
ask what printing process will be used and check with your printer
what are the file requirements. Some printers don't use Pantones, they limit you to certain colors of ink. That's why it's better to get that information first. Be reassured: it may look complicated but it's a challenging project too and it's very technical!