Bought these to soften up some rough edges on wooden pallet furniture and a few other wooden constructions. They worked perfectly, ripping into the wood and removing material instantly, so just what I wanted.
The first job I used one on though was to try and remove the finish from an old desk my wife was going to paint, but it proved far too aggressive for that, removing not only paint and varnish but also the outer layer of what turned out to be chipboard!
Although I have not used them on metal would imagine that they would make short work of any burrs or welding.
These are effective for heavy duty sanding, but not for more delicate work like paint removal from wood, where an orbital sander would provide a gentler, more controllable action.