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
Iron Butterfly, Frigid Pink and the Frost as already mentioned a great group.
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".