"Metalhead" is filmed in black and white, and it follows the plight of Bella (Maxine Peake) trying to flee from robotic "dogs" after the unexplained collapse of human society.

The episode's message has been widely debated, with reviewers discussing questions about artificial intelligence and the final shot of a box of teddy bears.

The plot and short running time have received mixed reviews, while Peake's acting and Slade's directing have been praised, along with the cinematography and the design of the dogs.

In a desolate landscape, Bella (Maxine Peake), Anthony (Clint Dyer), and Clarke (Jake Davies) drive to a warehouse searching for something to help ease the pain of Jack, who is dying.

[7] With Al Green as music editor, the soundtrack features compositions by Krzysztof Penderecki and includes some pieces which were used in 1980 horror film The Shining.

[5] The idea was suggested by the director David Slade to bring to mind old horror films and to match the "oppressive nature" of the episode.

[9] Brooker suggested using the Steven Spielberg films Duel and Jaws as inspiration, whilst The Texas Chain Saw Massacre was an influence for Slade.

[5] Slade reported that though biological events or apocalypses were considered, the episode does not suggest a backstory for the world in order to focus on the conflict between Bella and the dog.

[13] Brooker came up with the episode's central idea while watching videos of Boston Dynamics' robotics products such as BigDog.

[10] Collins came up with the idea that in the scene where the dog escapes the car wreckage, the release of its limb would be similar to the action of a drill chuck.

[7] The final scene shows a case full of teddy bears, which were yellow in real life but appear white in the episode.

[9] Brooker originally considered a gadget such as a Game Boy instead of a teddy bear, but Slade insisted on "something that you can touch, that you would hold to you, that would give you comfort".

[10] Jacob Stolworthy of The Independent suggested that it is the scariest episode of Black Mirror,[28] while The Verge's Bryan Bishop and his wife were "literally squirming" while watching.

[23] The episode has widely been described as a simplified version of The Terminator,[25][26][29] a 1984 film which—similar to "Metalhead"—is "about a human run ragged by an android's unceasing pursuit".

[30] It has also been compared to the "adrenaline highs" of Mad Max: Fury Road, a 2015 post-apocalyptic film which director George Miller wanted to shoot in black and white.

[29] Comparisons have also been drawn with the 2016 Anohni album Hopelessness, which "effectively communicates the cold horrors of drone warfare",[29] and the Philip K. Dick short story "Second Variety".

[30] Scott Huver of Variety noted that the episode is one of several monochrome works produced around the same time, with others including FX anthology series Feud, and "Gotta Light?"

[35] The episode can be seen to explore the AI control problem: Ed Cumming of The Telegraph questioned how one could "set limits on [the] ruthlessness" of a robotic guard dog.

[36] Another Den of Geek critic, Ryan Lambie, believed the dogs are not artificial intelligence, as their "lack of empathy or emotional nuance" is suggestive of "cold, pre-programmed logic".

[26] Before reaching the final twist, Harley suggested the episode could have been about health care in a world where medication is government-controlled and guarded by AI.

[12] Commenting on the teddy bears, Emily VanDerWerff said in Vox that the message may be that humans are "ruthless in some contexts and quite stupid and soft in others".

[24] According to Scott Beggs of Nerdist, the episode implies "toys and art are just as vital to survival as the other stuff at the bottom of Maslow's hierarchy".

[26] VanDerWerff suggested the scene evokes predator and prey imagery, comparing it to George Orwell's dystopia Animal Farm.

The website's critics consensus reads: "Though 'Metalhead' is the show's shortest installment, the bleakness of its plot and spareness of its thrills can often make it feel longer – though some may appreciate its claustrophobic beauty.

[38] Handlen praised her as "easy to root for", saying that Peake "does a good job of finding new ways to be terrified, angry, triumphant, and depressed".

[26] Sims praised that "every glimpse of the empty moors in high-contrast black-and-white photography jumps out at the viewer",[23] while Lambie commented positively on the ending's final landscape shots.

[36] Monty lauded the lack of exposition in the episode, believing it is the "strongest aspect" as the audience can make individual inferences about the backstory.

[36] Sims criticised it as "perhaps a little too cute"[23] and VanDerWerff called it "nonsensical", going on to write that it "lands somewhere between affectionate exasperation for humanity's foibles and a sick joke".

[37] Handlen was impressed by the special effects team's dramatisation of "what is essentially a box on legs", commending the "creepily real" design of the dog.

[30] Contrastingly, Oller found the dog's design and animation simplistic, commenting that it is "not the imposing, minimalist murder machine it needs to be".