The fourth wall is an entertainment convention originating from the theater, which imagines an invisible wall that separates characters in a film or video game from the audience. The audience can see through this "wall", but the convention assumes that the characters cannot, and are not aware of their fictional nature. Breaking the fourth wall is a fiction device that often establishes characters as aware that they are in a video game or film, sometimes looking directly at the player. Metroid, being a franchise of a rather solemn tenor, does not often break the fourth wall. However, several Metroid games feature at least a few instances of breaking the fourth wall, many of them being during the endings.
In the ending of the original Metroid, Samus Aran breaks the fourth wall as she looks directly at the player. If either of the two best endings are earned, in which she wears her one or two-piece bikini, Samus will remove her Power Suit, reveal her true identity and then wave to the player before the credits roll. This ending is referenced in Metroid: Samus Returns, if the game is completed on Hard Mode in under 4 hours. Samus will appear with her green hair and pink leotard and boots from the original Metroid, and wave to the player in the same manner as the original game.
The comical Victory Techniques for Metroid Japanese manga and strategy guide features Samus frequently breaking the fourth wall. She is seen playing The Legend of Zelda on her Famicom Disk System before landing on Zebes, and mistakes an Air Hole for a Warp Pipe from Mario.
In Metroid Fusion, pulling off a series of difficult Shinesparks to reach the Sector 4 Data Room before obtaining the Diffusion Missiles will allow Samus to bear witness to a unique conversation. The computerized Adam and the "Federation official" both laud Samus for using the Shinespark. As a reward, the official prepares to tell Samus about the Galactic Federation's secret project aboard the BSL Station, which Adam quickly shuts down. After establishing that Samus's objective is clear, Adam asks "I wonder how many players will see this message...?"
In Metroid: Other M, Samus congratulates the player depending on their item percentage, if it is above 25%. At 100%, she says "Perfect! Congratulations!"
There are multiple instances of Samus breaking the fourth wall in Metroid Prime 3: Corruption. When Samus acquires the X-Ray Visor, she appears to look directly into the camera and emit an audible gasp, implying that she can see the player with the visor. At the end of the game, as she is flying past the G.F.S. Olympus, Samus looks to her left (into the camera) and gives a thumbs up. Since there is no one else she could be looking at, it is very likely that her thumbs up is directed at the player. Lastly, she breaks the fourth wall as she is boarding her Gunship on the Main Docking Bay after removing her Varia Suit, by looking into the camera.
During the opening cutscene of Corruption, text including "corrupted" strings and data from the game itself, suggesting that it has been "corrupted" appear, breaking the fourth wall. This includes "V o u s m o u r e z .s i v otre". In French, this literally translates to "Y o u d i e .i f y our". This is a fragment of the French translation of the explanation of permanent Hypermode, displayed after Samus triggers her Auto Vent on Phaaze ("If your Phazon level fills completely, you will die.") As well, near the end of the sequence, there is another phrase: "m o u r r a i i i i i. ." This is basically "[I] will dieeeee...". Another phrase appears: "andrayda hat sich die Gestalt" German for "andrayda has ... herself the shape" (the verb would be at the end of the sentence, which is missing), this appears to be a part of the German translation of the description of Hunter Gandrayda's shape-shifting abilities. Another German word, Kämpfen (fighting), can be seen near the start of the data. The English words 'error' and 'danger' can also be seen in the data sequence, near the beginning. The words "Wii Format" can also be seen in the data. Numbers in hexadecimal format are visible at the bottom of the screen. In ASCII they read: "WAKE UP. WAKE UP. I AM AWAKESamus"