A metal rack is for holding things in the open where you can see them and reach them without opening a single door: pots over a stove, towels in a bathroom, coats by an entryway, pantry goods you actually use every week. It does the job a cupboard does, but faster, and it makes you deal with your own clutter because there's nowhere to hide it.
Before you buy one, measure the wall or corner with a tape measure, not your eye, because metal racks read as bigger and heavier once they're actually standing in a room than they do in a photo. Check the width against the full run of wall you want it on, not just the gap between two things, and leave at least a few inches of breathing room on either side so it doesn't look wedged in. For anything wall mounted, find the studs first and check the weight rating against what you plan to hang on it, since a rack loaded with cast iron pans needs more than a couple of drywall anchors and a prayer. Shelf depth matters more than people expect too: shallow shelves look neat but won't hold a stack of plates or a bulky basket, so bring the actual items you want to store and see if they fit before you commit. A rack that's open on all sides will always make a room feel lighter than a boxy cabinet, but that only works in your favor if what's on it is tidy, so be honest with yourself about whether you're a display person or a shove it on the shelf person. These suit kitchens, pantries, mudrooms, bathrooms, workshops and any room where you want things visible and grabbable rather than tucked away, and they're especially good in smaller or rented homes where built in storage is scarce and you need something you can take with you when you move. They tend to clash with rooms that are already busy with pattern or color, a metal rack full of odds and ends on top of a patterned wallpaper just reads as noise, and they don't belong anywhere you're trying to keep a cleaner, more finished look, like a formal dining room or a bedroom you want to feel calm. If you're starting with nothing, go for a simple, sturdy shelving unit in a kitchen or pantry first, black or raw steel rather than anything coated or fussy, since that's the one that will take the most daily use and show you quickest whether open storage actually suits how you live. I'd put the first one in the kitchen, somewhere near the stove where you reach for the same five things every single day.