It’s only really magnetizable metals that are a problem. I think they just say “ALL metals” because it’s simpler than asking people to work out what’s magnetic and what’s not, and risking they might (some almost certainly will!) get it wrong. Most rings are gold or a precious metal, so have no magnetic properties at all. The only problem with non magnetic metals is that they conduct heat very well, so could potentially get hot and cause a burn. But if they’re not on the part of you being scanned, that shouldn’t be an issue either - they weren’t doing your fingers, were they?
I don’t think I’ve ever had to remove my bra before, in spite of it having a metal clip, but belt was a no-no, because of the buckle. No way of knowing what it’s made of, but very likely steel, and therefore magnetic. I dunno what bra clips can be made of, but not steel, evidently. I didn’t even have the overheating problem of a small scorch mark where the clip had been, wasn’t conscious of it getting hot at all, even though I had my spine scanned. I was aware roughly which area the scanner was doing at any given point, as that part of me felt warm (and the noise moved around!), but no specific issues with the bra clip.