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.