A good metal lamp has a certain weight to it when you pick it up to move it, a solidness that tells you it will stay put when you brush past the table on your way to answer the door. Flip the switch and there's no wobble, no rattle, just a clean click and light that lands exactly where the shade points it. Run a thumb down the base and you feel a seam or you don't, and that one detail tells you almost everything else about the thing.
Where metal falls short is anywhere you want softness, visually or otherwise. A bedroom that already leans cold, lots of gray linens and bare floors, doesn't need another hard surface throwing light around, and a metal lamp next to a bed you're trying to make feel warm can end up working against you. Metal also holds heat differently than ceramic or wood, so a base near a radiator or a sunny window can get surprisingly warm to the touch, worth knowing if you've got a toddler who grabs everything at eye level. And if the room already has a lot of metal, a shelving unit, a black framed mirror, exposed pipes, adding another chunk of it can tip a space from industrial into just plain cold.
The difference between a lamp that lasts and one that ends up in a donation pile usually comes down to what's happening at the joints, where the base meets the stem and where the stem meets the socket. Cheap ones use thin stamped metal and a single screw that loosens over a year of being switched on and off, so the shade starts to tilt no matter how many times you straighten it. Better ones are either solid cast metal, which has real heft, or a thicker gauge tube with welded or properly threaded joints, and you can usually feel the difference just by lifting the thing off a side table. Finish matters too. A painted finish can chip at the base where it gets knocked against furniture legs, while a true plated or powder coated surface shrugs off that kind of daily contact for years.
For living with it day to day, I've always found brass and warm bronze finishes the easiest, they catch light instead of just reflecting it flatly, and they read as warm even in a room with cooler colors elsewhere. Matte black is close behind, forgiving of fingerprints and dust in a way polished chrome never is. Chrome and nickel look sharp in photos but show every smudge, so they ask more of you than the others. A brushed finish in any of these tones will hide more daily wear than a high gloss one, which matters more than people expect once the lamp is actually living in your house and not just sitting in a showroom.
If you find one with good weight, tight joints and a finish that doesn't flinch at a little dust, it will likely still be switching on reliably long after the lampshade itself needs replacing.