Forgotten heavy bands from late 60's to early 70's


Have been a fan of hard rock/metal since high school. Always liked the heavy/physcadelic bands equally to the metal bands I grew up with Ozzy-Maiden and Scorpions ect. Recently on Youtube I discovered some heavy/physcadelic bands I was unaware of. 13th Floor Elevators-Five Day Rain-Probe Direction-The Hook and Vahalla. Are these bands albums worth persuing? Feel free to mention any other band that deserves to be heard. Look forward to your responses.
dayglow
Some Detroit area bands to seek out for that time frame: Iggy and the Stooges "The Stooges" "Fun House" "Raw Power", MC5 "Kick out the Jams", Frigid Pink "Frigid Pink".
Atomic Rooster, "Atomic Rooster" and "Death Walks Behind You" ... killer stuff. Also check out Jade Warrior, though perhaps more avant garde than heavy. Also check out Man, "Live at the Padget Rooms, Penarth", "Christmas at the Patti", and "Maximum Darkness".
The name will not shock anyone, but Deep Purple. I only mention this because I dusted off/played their Shades of Deep Purple album last night. This is their lineup w/Nick Simper on bass, and Rod Evans on vocals. Although Jon's keyboards are easily distinguishable, it is very different than the mk. II lineup.
I found this to be an interesting listen. They do a version of I'm So Glad, which of course makes one think of CREAM. It's actually a Skip James tune, which I learned while reading the album cover. I really have to be in the mood for Made in Japan..., but Shades less so.