I've always considered Rush prog metal ( a more tame version) after their first 2 lps...and Iron Maiden is certainly metal/prog metal to my ears. I also think a few of the earlier Porcupine Tree lps qualify but they are more prog than metal. I dont always agree with how PA website lists these bands.Another useless list. lol
How you can make such a list without Rush's Hemispheres or Yes' Close To the Edge is crazy.
@Dr. Wu...I think Queensryche really has only one album that I would consider progressive, and that's Rage For Order. I think they pushed some traditional metal boundaries on The Warning, but I don't know of that one's for you. And personally, I don't consider O:M a progressive record at all, but it is an amazing album nonetheless.
I dont think Yes belong in prog metal at all....even though there are a few 'heavy' moments on CTTE, they are one of the big 6 of prog rock according to most prog fans.
This is Prog Archives official page on prog metal (though others might disagree with some choices)