In Brightburn, there are five other meteors in addition to Brandon's, and there are many theories about what those meteors are. While every theory has an explanation, not all of them are equally plausible. At the same time, it seems that each theory must share at least one thing—that the meteors, like Brandon's, are all spaceships. It is possible that the six meteors are not all spaceships, and it is also possible that Brandon's meteor ship is not related to the others at all. It could be that his ship was simply caught up in a passing meteor shower. Anything is possible in movies, but it seems more likely (and more interesting) that they do share this important detail. Additionally, Brightburn's post-credits scene, featuring Michael Rooker playing a conspiracy theorist, implies that the other five meteors are spaceships, a theory with which one of the film's stars agrees.
Brightburn is a superhero horror movie about how 12-year-old Brandon Breyer (Jackson A. Dunn), becomes a national supervillain. He begins to discover his powers when his now hidden meteor ship starts to communicate with him. This causes him to act strangely; his adoptive mother, Tori (Elizabeth Banks), believes it's because of his alien origins. She does a web search for "Kansas meteors 2006" and learns that a total of six meteors arrived during the "celestial phenomenon" over Brightburn that brought Brandon. Aside from this, there's little information in the movie about Brandon's meteor and even less about the other five. However, because they are related to each other through the celestial phenomenon, it is more likely than not that they are all spaceships, which Brandon's meteor clearly is. It is also more likely than not that the five other meteors, like Brandon's, are not on Earth by accident.
It's important to acknowledge that Brandon's story is a direct reference and an analogy to Clark Kent's (Kal-El) story. The supervillain Brightburn (Brandon) is obviously an evil version of Superman (Clark). Brightburn's filmmakers, James Gunn and director David Yarovesky, are admitted superhero fans and created the movie as an homage to what they love about superhero and horror movies. Logically, many assumptions made about the meteor ships in Brightburn are likely to incorporate what viewers already know about Clark. In many versions of Clark's story, he is sent to Earth in an escape pod by his benevolent parents to save him from Krypton's destruction and become Earth's champion. Luckily, Clark is found by equally benevolent adoptive parents, Jonathan and Martha Kent, and fulfills his destiny. Every theory about the other five meteors in Brightburn is likely to be some version of this escape pod story.
The Other Five Meteors Are Escape Pods (Like Brandon's And Clark's)
If the other five meteors are anything like Clark and Brandon's meteor ships, they are likely to be escape pods intended to preserve the lineage of their senders. This would mean that they are all most likely from the same place. What it wouldn't mean is that they would all have the same philosophy and powers, given that they might not come from the same species or society. Like Superman's Krypton, which had many rival factions, these escape pods might be the offspring of rival factions wherever they come from.
The philosophy of Brandon's senders is clearly to "take the world," and it seems likely that the two supervillains Michael Rooker's character mentions in the post-credits scene share this philosophy. This could either pit them against each other or enable them to join forces. The remaining three meteor ships could then contain either supervillains or superheroes. This is the most likely scenario because it is the closest to the Superman analogy, but it is far from the best possible scenario in terms of entertainment.
The Other Five Meteors Are Gestational Pods (Alien Eggs)
Early on in the movie, Brandon is at school in a classroom where his teacher asks about the difference between bees and wasps. Brandon answers the question and goes on to provide more information about wasps, in particular wasps that practice brood parasitism. Brood parasitism is a natural phenomenon in which a life form leaves its offspring to be raised by a host life form, usually to the detriment of the host. Clark Kent's story is a loose analogy to brood parasitism, but Brandon's story fits it almost perfectly. The phenomenon has also been used in movies like Vivarium and The Village of the Damned to great effect.
If the other five meteor ships are gestational pods being used as a part of their inhabitants' life cycles, then it would make sense that they all came together. Unlike the escape pod theory, however, this theory makes it more likely that the meteors' inhabitants come from the same species. However, it doesn't guarantee that they would necessarily have the same agenda for Earth. This is somewhat problematic because it reduces the meaning of the meteors to a simple biological imperative rather than a clash of civilizations. On the other hand, that's also what makes it interesting in a disturbing way.
The Other Five Meteors Are Biological Weapons
The other five meteors could be biological weapons. If Brandon and the other two supervillains from the post-credits scene are a good example of what are in the other three meteors, then it's plausible that they have been sent to Earth as either a first wave of an invasion or as the invading force themselves. This would mean again that they all come from the same place, but unlike the escape pod and alien egg theories, it would also ensure that the senders of the meteors are working together toward a common goal. Solitary alien visitors are often depicted in movies as being either benevolent saviors or messengers of conquest. The biggest problem with this theory is that it would transform the promising Brightburn franchise into an alien invasion series.
The Other Five Meteors Are Part Of A Bigger Story
The most compelling theory for the other five meteors, especially if a Brightburn 2 is made, is that they are a mix of different things and will introduce a story completely independent from the Superman analogy. Brandon's meteor was a ship that most likely brought him to dominate Earth, otherwise, why would it beckon him to "take the world"? The other two supervillains mentioned in the post-credits scene could be Brandon's allies, his enemies. or indifferent to him. What is certain about their meteors—if they did arrive in meteors as the post-credits scene suggests—is that they are passenger ships, like Brandon's. The remaining three meteors could contain anything, although the post-credits scene implies that at least two of them had passengers and one is a complete unknown.
The squares next to the face Michael Rooker's character in the post-credits scene display six figures: Brandon as the Brightburn supervillain; the aquatic supervillain in the South China Sea; the rope-wielding female supervillain; an unknown character wearing a red suit; an unknown alien; and a question mark. The square featuring the question mark could indicate that the meteors may have brought something other than super-powered life forms to Earth. This theory about the other five meteors in Brightburn is the most compelling because it would give the world a new superhero franchise that stands on its own rather than just as an adaptation of Superman, one of the world's most popular superheroes.