Should you see it? Yes. Repeatedly. It's my favorite bad film.
John Agar has a reputation for having been in a lot of turkeys and, if I review every film I want to on this blog, his name will appear from time to time ("Zontar," at the very least). This has one of his more hammy performances.
The film has nuclear physicist Agar turning on his Geiger counter and it's screaming. He points it out the window and says it must be coming from the mountain in the distance (the more science you know, the funnier that is). He goes to the mountain, into a cave and there meets, fights and is taken over by a giant disembodied floating brain with eyes. Agar then goes on to develop shiny silver eyes and he uses them to shoot down airplanes, while chuckling. The alien in Agar gets the hots for Joyce (not Jayne - I've made that mistake) Meadows. Another disembodied brain comes to Earth, takes over Agar's dog (!) and battles the one in Agar. Meadows and Agar then kill the bad brain with an axe and all is well.