The exposition and set up for this film apparently try to set up a basis for an OSI/"A Men" movie franchise, but that seems to have fallen by the wayside as so many decent ideas do. Still, even as a "one shot", this is a solid effort. "Magnetic Monster" trots out an unusual plot that acts as a sort of "science fiction/police procedural" story. It was probably very unusual and experimental at the time, but it worked pretty well. In fact the plot still has echoes today in unexpected places (like many of the later "Star Trek: TNG" episodes.)
To tell the truth, I was expecting the so-called "Magnetic Monster" to be an actual creature on the lines of "the Flying Claw" or Godzilla, but the screenplay surprised me by making the "science gone wrong" aspect of the plot be a new "atomic element" with magnetic properties that violently turns energy into matter, and doubles in size and violence ever time this happens. In this, the movies predates even classics like "The China Syndrome" by using atomic energy and radiation itself as an agent of global disaster.
The best thing about the film is the way the central mystery builds from a seemingly innocuous event (all the clocks in a department store stop and the manager and the clerks are indignant and horrified by the magnetic antics of their metal items) to hints of a more serious problem, and then (through clever detective work) finally uncovering a world threatening danger. Richard Carlson works hard to sell his role, and the movie features a number of familiar character actors who also fill out their parts admirably.
The only real glitch in the screenplay involves the final scenes with the "Deltanator" (a technological marvel imported via stock footage from another, older movie); it is clearly established that the "magnetic monster" must be bombarded with "900 millions volts" of power in order to destroy it before it becomes unstoppable, and the "Deltanator" is supposedly the only device in the world powerful enough to generate that much; elaborate,frantic measures involving high speed military jets are employed to get the material to the machine before the deadline passes...but once Carlson and his assistant get to the machine, the head technician informs them that the Deltanator can only generate "600 million volts". Of course, this was thrown in just to generate a little suspense, but it makes it hard to suspend disbelief. "6" sounds nothing like "9"...and with the world at stake, you'd think someone would have double checked the numbers. Also, in an effort to generate more of a final climax, the head technician seems to have a psychotic break, and tries to sabotage Carlson's efforts to drive the machine to its peak...you can't help but think, "Excuse me? End of the world mean anything to you, Mr. Technician guy?". It just makes no sense, and so the film is less than it could have been.
Still, glitches aside, this is a fine little movie that tries to treat its subject, and its audience with respect. I liked it a lot.