Some people say that Linkin Park is rock, some of it is, but not most of it, its early albums, Hybrid Theory, and Meteora, is rap rock and nu metal, in my honest opinion, its average genre is alternative metal, what bothers me is when people say it's pure rock, because thats not necessarily true
Linkin park might be metal, it might not be, it's simply music. It's quite annoying to see lots of people trying desperately to categorize music, especially when the band in question has a unique style. Unfortunately this happens quite a lot with labels such as "metal" and "electronic". As for the person saying "some people say it's rock", metal is in fact a sub-genre of rock, so you will have to be more specific.