A metal storage cabinet should look like furniture, not like something that escaped a school gym. That's my one firm rule here. The cheap ones read as equipment, all bare sheet metal and visible screws, and they sit in a room like they're waiting to be reassigned to a supply closet. A good one reads as a piece, same bones, totally different attitude, and that difference is almost entirely in the finish.
In an ordinary room, a metal cabinet works best doing a job a wood piece can't quite do without looking fussy, a boot and coat situation by the door, craft supplies in a home office, linens in a hallway. It sits well next to warmer materials, a wood console, a woven basket, something with grain or texture to keep the metal from feeling cold and institutional. If you've never owned one, start with a plain two door cabinet at roughly waist height, nothing with a dozen drawers or a lock you'll never use the key for. That size does the most work and you can always add a second piece once you know where you actually need the storage. For color, I'll push you toward something with a little nerve, because flat white or gray metal cabinets have a way of disappearing into looking cheap even when they're not. A deep forest green, a soft terracotta, even a matte black, all read as intentional in a way that beige metal never will. My mother has a putty colored one in her mudroom and it looks like a filing cabinet that wandered in from an office. Mine is a mustard yellow one by my back door and a client once asked where I got it mid haircut, scissors still in hand.
The difference between the good version and the sad version shows up the second you open the door. Cheap cabinets have doors that rattle, hinges that squeak within a month, and a powder coat finish so thin you can see the metal through it at the corners within a year. A well made one has a baked on finish that feels slightly textured, not slick plastic, hinges with real weight to them, and shelves that don't bow the first time you load them with books. Check the back panel too, a flimsy one will dent if you so much as lean a vacuum against it. The welds should be clean, not blobby, and the whole thing shouldn't wobble if you push on one corner.
A metal cabinet in the right color stops being storage and starts being the thing people notice first.