King Crimson, Yes, and Pink Floyd are all progressive rock acts. So I'm going to recommend metal bands that incorporate similar elements.
As such your best bet is Dream Theater. They are a progressive metal band thats been around since the 90's and are amazing. Their most well known song is Pull Me Under which is more straight forward metal than most of their stuff. After that try Octavarium (20 minutes long), The Glass Prison, or On the Backs of Angels for a good sample of their work.
If they aren't hard enough then try Tool. I've heard some describe them as metal Pink Floyd. They are another progressive metal band who put massive amounts of thought and detail into their music and use funky time signatures and often shift time signatures within the same song. Try Schism, 10000 Days, Lateralus, or Aenima.
Lastly try Nightwish with some caveats. Nightwish is a symphonic metal band but they are similar to progressive metal in their music only they incorporate orchestra and classical instruments into their music. The caveat with them is that they've had three different lead singers which could be confusing to someone unfamiliar with them. IMO their current singer is the best as she can sing anything whereas the first two were very limited in scope. If you look them up on youtube add the word "Floor" to the end of your searches which will give you performances with their current singer Floor Jansen. Then be prepared to have what fans refer to as a Floorgasm when you are in awe of her singing and belting ability. The Floorgasm of this song begins at about the 7:30 mark and climaxes at 9:22. When I watch this live performance it reminds of Queen at Live Aid where they have a massive audience just eating them up and handbanging and arm waving in unison. Nightwish is HUGE in Europe where they play places like Wembley and headline festivals like Wacken Open Air (where this video was taken) but play clubs in the US (where I've seen them twice). Other songs to try by them with Floor singing would be Romanticide, Song of Myself, Poet and the Pendulum, and Greatest Show on Earth.