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 put out an album later in the 70's called Metamorphosis. This album was a sea change for them, different music than from their Inna-Gadda-Da-Vida days. Three of the four original members remained but they added two guitarists, one of whom played slide guitar. It retains the heavy sound but branches out in style and playing. The album has a picture of mountains with two coffins on one of the mountains.
I wouldn't call them forgotten (maybe not so well known in the US), but I have to mention Hawkwind. Space Ritual is the ultimate heavy psychedelic album.
Blue Cheer, Spirit, Love...all amazing and well ahead of their time from 1966 to 1969.
Thanx for the many great selections. Sir Lord Baltimore-Boulder Damn and Night Sun are great bands that I was unfamiliar with. Also discovered Armageddon-st-1975. If your familiar with Armageddon is it worth the effort and cost to obtain an import pressing?