If you were a film director with dreams of being a military general, the “Transformers” movies would be your best job ever.

That’s certainly the way Michael Bay treats the gig. Bay’s movies express a childlike love of military stuff, especially the parts where tough-talking guys bark out orders and large vehicles explode.

With their mind-boggling array of moving parts, the “Transformers” pictures are a great reward for a director who seems like he’d be happiest playing around with G.I. Joes in the sandbox.

Bay has now made five of these things. Even at their best (Part 3 was wild fun), they are ludicrous and insane.

The fact that they’ve been popular will astonish and puzzle future generations, much as the presence of the Transformers is bewildering to the Earthlings of the films.

“Transformers: The Last Knight” ties the existence of the giant robots to the King Arthur legends. Of course it does. Merlin the magician (Stanley Tucci, camping it up) procures an amulet with superpowers, yadda yadda yadda, a thousand years later Mark Wahlberg puts it around his swollen bicep in order to save planet Earth.

I’m fine with having Mark Wahlberg be in position to save Earth, but the rest of “The Last Knight” is unintelligible. There’s a dotty English lord (Anthony Hopkins, also camping it up) and a super-hot professor/love interest for Wahlberg. You may think the latter part is played by a digital re-creation of Megan Fox, but the credits insist it is actress Laura Haddock.

The humans (including returning comic relief John Turturro) are dwarfed by the Transformers, those hulking heaps of metal bric-a-brac. I understand why kids enjoy these entities, but I don’t understand why Michael Bay loves them, or why he seems so emotionally involved in the nobility of Optimus Prime and the chicanery of Megatron.

Also hard to understand: why a movie for kids has a steady stream of profanity throughout (but not the one word that would trigger the R rating). I guess leaving out the cussing would interfere with Bay’s fantasy bro-world.

Bay destroys more of the world than usual, as a huge metal quasi-planet approaches and then strikes our planet. The best of these giant-scaled visions is the moon getting raked by the humongous contraption.

I’m not sure the science holds up, but the movie ridicules science anyway — people are stupid if they think physics will solve the impending global disaster, rather than the magical amulet from King Arthur’s time. I suppose on this one point, “The Last Knight” is an accurate depiction of the world today.

Michael Bay really is an amazing field general; there are moments when you marvel at how many things are happening in the same five-second shot. Given that all this energy is expended on something this vast and witless, “The Last Knight” may be the most depressing movie of the year.

“Transformers: The Last Knight” (1 star)

The fifth of director Michael Bay’s giant-scaled series is even more witless than usual, as Mark Wahlberg and Anthony Hopkins try to save Earth from the robot planet drifting our way. Bay is an amazing field general, but watching this much energy expended on something so infantile is a depressing experience.

Rating: PG-13, for language, violence

Opening Friday: Alderwood, Alderwood Mall, Cinebarre Mountlake Terrace, Everett Stadium, Galaxy Monroe, Marysville, Stanwood Cinemas, Meridian, Oak Tree, Pacific Place, Sundance Cinemas, Thornton Place Stadium, Woodinville, Cascade Mall, Oak Harbor Plaza