rust can poison you and contaminate your food, besides being unsigltly and dirty

ever think of stainless steel? talk to your restaurant supply house

also i have seen flormica products that look metalic, all shades and colors available, where you could get a dark metal look and have sanitary and safe surface

if you must for some reason go with this idea of yours of real metal, you could heat treat it to blue it up although it would not be an even coloring, that may what your looking for and also could warp

do you know that sheet metal is also very expensive compared to other materials. 2×2 ft of 1/8″ mils steel is about 50 bucks

you could apply a clear coat of laquer or polyurathane although this could also chip and contimante you food further, requireing constant touch up

go with the simulated steel formica is my advice

look it up on internet, probally find sample colors on some web site somewhere, perhaps post the link here after u find it so others can look