It clicked for me on a narrow apartment balcony, the kind you get in a one bedroom where the landlord calls it "outdoor living space" and means a slab big enough for two chairs if you're friendly with your neighbor. I put a little round metal table and two chairs out there, the folding kind, and suddenly it read like a room instead of a storage ledge. That's the thing about metal outdoor furniture, it does more with less space than wood ever will, because the legs are thin and the whole thing has less visual weight.
Where it goes wrong is when people treat it like indoor furniture and plant it next to a wicker sofa or a heavy wood dining set, like three materials are going to have a nice long chat. Metal wants company that's simple, a plain tile floor, a wood deck, concrete, grass, that's it. Pair it with another heavy textured material and the whole patio starts looking like a showroom that got rained on. I made this mistake with a rattan loveseat and a metal bistro set on the same deck for about a summer, and it never once looked like I meant it.
Sizing is where people actually lose money, because metal furniture photographs small and sits bigger than you think once four chairs are pulled out from a table. Measure your actual clear space, not the footprint of the table alone, leave at least two feet behind every chair for someone to stand up without elbowing a railing, and if you're working with a balcony under eighty square feet, go for a bistro set over a full dining set every time. A round table also saves you a scraped shin compared to square corners in a tight spot, learned that one the hard way, more than once.
If you're starting from zero, a bistro set is the easiest first move, two chairs and a small table, because it works on a balcony, a porch, even a kitchen nook if your indoor dining space is small and you're the type to get a little dramatic with your decorating. Powder coated steel in a real color, not another sad black or white, is the one bold thing I'd tell you to do here even if you're not ready to paint anything green yet. A client of mine put a mustard yellow set on her fire escape and said three different neighbors asked where it came from. That's the kind of return a wood chair never gets.
This suits anyone working with a small outdoor space who wants it to look finished without needing a truck to deliver the furniture.