There are two main classes of Metroid games,

Type I Metroid games, originating with Metroid NES (includes Super Metroid, Metroid Prime, and Zero Mission),

and Type II Metroid games, originating with Metroid II Return of Samus (includes Metroid Fusion, Other M, and Samus Returns).

Type I Metroid games have a classical gamestyle with classical items, with a focus on speedrunning and sequence breaking. Type II Metroid games are more linear, less speedrun-friendly, and far more story driven. They often feature different items and styles as compared to previous releases, and are far more experimental.

These generally follow a similar pattern:

Spiritual successors:

Super Metroid is a spiritual successor of Metroid, re-exploring Zebes in a grander scale, and then exploding it at the end. You re-face original enemies and old bosses, but the concept is completely the same: Kill the bosses, unlock Tourian, and kill Mother Brain.

Metroid Fusion is a spiritual successor of Metroid II, exploring the BSL (which is itself built off of SR388), and then you explode SR388 at the end. You re-face original enemies and old bosses, but the concept is completely the same: Unlock wacky new items, kill the bioweapon that threatens the galaxy, and escape with some loving creatures.

After you release your spiritual successor, release your...

3D Remakes of the Spiritual Successor

Metroid Prime and Super Metroid can both be described as follows: Samus responds to a distress call on a derelict spaceship. Going through the ambient death and decay she finds Ridley, who escapes to a nearby planet and rigs the ship to explode. Samus tracks him down to said planet, where the Space Pirates are doing wild fuckin experiments on Metroids. She lands in this ambient rainy foresty grassy place and gets to work, defeating all the bosses so she can unlock the Final Level. Both games feature a trek through the derelict spaceship, which has crash-landed and is now partially underwater, and connects two parts of Brinstar/Tallon IV. The final boss is pretty easy, until you get its second form, which requires the hyper beam to defeat. They're the same game!

Metroid Other M and Metroid Fusion cab both be described as follows: Under command of Adam, Samus explores a Galactic Federation research facility where they're experimenting on Metroids. Samus links up with Adam at hubs, gets info, directions, and powerups as she explores the compartmentalized spaceship. Different sections/biospheres have different themes. She defeats Nightmare, a reborn Ridley, and sets the station to explode so she can stop the Federation from using the Metroid baby for bioweapon research. The Metroids are just too dangerous to research on, you see. Both games are very story driven, have Samus monologues, and are considered kind of black sheep of the series.

After releasing the 3D remake, then you gotta release...

An actual remake of the original.

This section is a lot more straightforward TBH. Metroid: Zero Mission and Metroid: Samus Returns are remakes of the original that expand in pretty similar ways. (See also: AM2R)

There are hella similarities I missed in this writeup, and this categorization misses Metroid Prime 2 and Metroid Prime 3, which don't fall into either of the two categories. (One might argue that Prime 3 and Prime 2 are Type I and Type II, respectively...) I had this theory before Other M (and then, eventually, Samus Returns) was released, and it made me happy to see those two games round the theory out completely. But now it has no predictive power.

Others have argued that Metroid Prime 2 is just a Zelda game (become the Hero of destiny and use the power of Light to save the two parallel universes from splitting!) and Metroid Prime 3 was almost an open world game. In that vein, Prime 1, 2, 3 is almost OoT, MM, and TP, but, shrug, right?

Maybe it will be that Metroid Prime 4 will just be Metroid Prime 1 Two: Electric Boogaloo, because that's a really successful formula. Who knows?

I'm done with this post thank you for your time