Late winter is when I notice metal shelves doing their best work, those gray afternoons when the light coming through an old window is flat and a little unkind, and you want something in the room that doesn't ask to be softened. A set of metal shelves against a plaster wall that's seen a hundred years of this kind of light looks like it's always been there, even if you put it up on a Tuesday afternoon with a cordless drill you borrowed from your neighbor.
I'll say plainly where they're the wrong call. If you've got a nursery, or a bedroom you want to feel like a place you actually sleep rather than a place you store things, metal shelves read cold fast, especially the thinner gauge ones that ring a little when you set a mug down on them, a sound I never love hearing at six in the morning. They also don't forgive a crooked wall the way wood does, a warped old house wall will show every gap at the back where the unit doesn't sit flush, and in a house like mine, built when plumb lines were more of a suggestion, that matters. Measuring is where most people go wrong with these, I've done it myself, bought a unit built for a modern ceiling height and ended up with eight inches of dead air above it that just collected dust and regret. Measure your actual clearance, not the room's advertised ceiling height, leave at least three inches above the top shelf for breathing room, and before you buy, figure out what you're actually putting on it, books want shelves closer together than you think, a stack of serving platters wants the opposite, and a unit with fixed shelf spacing will punish you either way. Depth matters more than most people plan for too, anything deeper than fourteen inches in a small room starts eating floor space you didn't know you needed until it's gone.
Where they genuinely sit well is in a room with some age already doing the talking, old brick, bare wood floors, a worn leather chair nearby, because the plainness of the metal gives the old stuff somewhere to rest its eyes, so to speak. They look wrong next to anything fussy, carved frames, ornate lamps, a lot of gilt, the two styles just argue with each other across the room. Put a stack of linen next to a cast iron pot on one shelf, a few books leaning sideways on another, and the whole thing starts to feel lived in rather than assembled.
For a kitchen, a mudroom, or a workroom where you want to see what you own and trust it'll hold, I'd take a good metal shelf over almost anything else in the house.