When I was growing up Prog Rock had a somewhat different definition. I guess some of it might have been classified as Proto metal, but for the most part it was know for a definite sound based around the keyboard.

Bands like Hawkwind were experimenting extravagant stage shows. Of course Lemmy would go on to become a metal icon, and members of the band are still performing.

Early Nektar had a trippier electronic sound, and they've stayed pretty true to it.

Eloy had heavier sound. They've also stayed pretty true over the years.

Bands like Genesis were the mainstays of progressive rock, and Steve Hackett recently released a new disc.

Strawbs was one of the odd ones, more folksy than the others I was listening to in the early 70s.

Manfred Mann's Earth Band started out with a bluegrass sound and slowly morphed. His cover of Bruce Springsteen's Blinded by the Light was his biggest hit.

And, of course, no list would be complete without Emerson, Lake and Palmer. and Yes.

I could go for quite awhile longer, but this gives you a taste of the seminal groups that founded the genre. I'll add one more because he's generally attributed as pioneering the stage show.