On July 20, 1969, during the last phase of the Apollo 11 mission to the Moon, a robotic eye emerges from the lunar soil and takes notice of the landing module as it takes off. The eye buries itself again.
Decades later the Space Shuttle Camelot encounters a derelict spaceship in orbit around Earth. Mission commander Colonel Jason Grant (Walter Koenig) leaves the shuttle to investigate. He discovers a reddish-brown pod and a mummified human corpse. Both things are brought back to Earth, where it is found that they originated on the Moon some fourteen thousand years ago. Shortly thereafter, the unattended pod comes to life. It builds itself a cybernetic body with parts from the lab and pieces of the ancient corpse. The cyborg kills a lab technician and exchanges fire with security guards before Grant destroys it with a shotgun blast to the head.
Using the last completed Apollo rocket, Grant and fellow astronaut Ray Tanner (Bruce Campbell) go to the Moon on a search-and-destroy mission. They discover the ruins of an ancient human civilization. Inside, they find a woman in suspended animation who identifies herself in a rudimentary fashion as Mera (Leigh Lombardi). Mera later reveals the name of the killer cyborgs — the Kaalium. They survive the attack of a spider Kaalium and return to the landing module, with Mera wearing her own spacesuit but it turns out that the Kaalium have stolen the module. The Kaalium also shoot down the command module, leaving the astronauts stranded on the Moon. In subsequent attacks by the Kaalium, Tanner is killed, Grant and Mera are taken prisoner, and the Kaalium head to Earth.
Grant frees himself and rescues Mera from certain death at the hands of a cyborg. In the meantime, the Space Shuttle Intrepid is launched to intercept the approaching alien ship. Grant and Mera look for the control room and find the landing module, which has been adapted into the alien machinery. Grant supposes the module was the last piece of equipment that the Kaalium needed to complete their ship. He starts the module's self-destruct sequence and as they are attacked by a Kaalium crew member, discovers that he can use his gun as a rocket to get away. He and Mera exit through a breach in the hull. The ship explodes after they have reached safe distance.
Some time later, Grant and Mera are shown as a couple living on Earth. Mera, having learned to speak English, explains that she was put in stasis to warn others about the Kaalium. Grant tells her that she does not have to worry anymore, that it is over and hugs her. However, one of the pods survived the explosion and is now in a junkyard preparing to build itself a new body.
As the end credits finish rolling, a brief audio clip is heard of Grant talking to a NASA official on the phone about the possibility of any debris that may have fallen to Earth in the aftermath of the ship's explosion. The official denies such a thing and assures Grant that anything that would have crashed to Earth would have incinerated upon entry.
Moontrap received mixed reception from various critics. As of March 2016, the movie held a 29% fresh rating at Rotten Tomatoes. IMDB gives the movie a 5 out of 10. DVDtalk had a higher opinion of the movie, stating that for a low budget picture it often exceeds expectations.In its review of December 27, 1989, Variety stated "Moontrap is a very entertaining though highly derivative sci-fi adventure ... this one's a goodie ... Moontrap is exciting and suspenseful."
A Blu-ray DVD was released on the 25th Anniversary of the movie in September 2014. The movie had previously only been officially released on VHS.
On April 17, 2011, Robert Dyke and Tex Ragsdale launched a fundraising campaign for a Moontrap 2 graphic novel that would be adapted into a movie. The project was intended "to act as a presentation device to show potential backers of the hoped-for film what it's going to be about. More effective than a script alone in that it not only tells the story but shows what the film will look like." However, due to lack of contributions the project was cancelled on June 1 of the same year.
In early 2014, another project was announced by Robert Dyke and Tex Ragsdale. On February 5, a Facebook account was created for Moontrap Target Earth. The first post said, "Watch this space for news about Moontrap Target Earth, now in pre-production with the original Moontrap creative team." Two days later, a post on the Moontrap Target Earth page confirmed the legitimacy of the new project: "Moontrap Target Earth is not a direct sequel to the original feature but, instead, a new stand-alone adventure." The plot is described as "an archaeological dig uncovers a long-buried spacecraft from an ancient, advanced human civilization. A young woman studying the ship suddenly finds herself transported to the Moon, to unlock an ancient mystery." Pre-production began in February and filming commenced in April at the Motion Picture Institute in Michigan.
The cast includes Sarah Butler as Scout, the main character; Charles Shaughnessy as Richard Kontral, the ruthless agent of a shadowy organization; and Damon Dayoub as Allen, an adventurer who joins a mission to expose a world-changing secret. Other cast members includes Niki Spiridakos, Tarick Salmaci, Chris Newman, Jennifer Kincer, Jon Ager, Cara AnnMarie, and D.B. Dickerson.
On February 7, 2017 Sony Pictures Home Entertainment released "Moontrap Target Earth."