|This article is written from the Real Life point of view|
- This article is about the series' main theme. For other uses, see Title (Disambiguation).
The Title theme consists of a six-note leitmotif, which can be broken down into two three-note phrases. The first phrase consists of an ascending minor sixth interval followed by a descending perfect fourth interval. The second phrase consists of an ascending minor seventh interval followed by a descending major second interval. There may be additional patterns added, such as harmonies or repeated notes, but this pattern will always remain the same.
Since its debut in the original Metroid, the Title theme has been reused in multiple subsequent music tracks, appearing in every game except Metroid II: Return of Samus and Metroid Prime: Federation Force. In most instances, it can be heard in the game's respective Title Screen themes, but is also heard in other tracks, such as Chozo Shrine and Metroid Prime Battle. Therefore, this leitmotif can be considered a main theme for the entire Metroid series.
The title theme of Metroid set the formula for future Metroid games to follow. It opens with the dark and mysterious Title leitmotif, then transitions to a lighter section. This original version would be later remixed in Kid Icarus / Metroid Original Soundtrack Orchestra Version, Brinstar (Melee), Depth of Brinstar, Metroid: Zero Mission, Video Games Live, WarioWare D.I.Y., PLAY! A Video Game Symphony, and Super Smash Bros. for Wii U.
The leitmotif received its first remix in a Metroid game with Opening (Destruction of the Space Colony) of Super Metroid. After a tense opening, a slow and foreboding version of the Title theme is heard. This version is also orchestrated in A Symphonic Poem and Into Red, Into Dark. However, when Opening (Destruction of the Space Colony) was remixed in Zero Mission, it was without the inclusion of the six note Title theme.
Metroid Prime features multiple remixes of the Title theme. The Metroid Prime Theme incorporates the Title leitmotif, played by a high-pitched flute-like synth instrument and distorted with heavy static; this version is also remixed in Metroid Prime Hunters: First Hunt and Super Smash Bros. Brawl. Chozo Shrine has a calmer and more serene version of the Title theme. Metroid Prime Battle is the first time that the Title leitmotif was incorporated into a boss theme, with this version sounding aggressive and climatic; this version was later remixed in Metroid Prime Pinball.
The Title theme of Metroid Prime Hunters is darker in tone, and the notes are higher-pitched and given reverb. It can be heard here:  Another version of the Title leitmotif is heard during Hunters, performed with a classic sci-fi synth instrument. Gorea Returns features another boss remix of the Title theme, sounding very similar to Metroid Prime Battle.
While the Title leitmotif is not clearly heard in MP3 Title Music, the title theme of Metroid Prime 3: Corruption, the extended version heard during the credits opens with a haunting version of the six-note theme sung by a female choir. This was also performed live by the State Choir of Latvia during the Symphonic Legends concert. This is the only version of the Title theme included on the Samus Archives Sound Selection CD.
The compilation rerelease Metroid Prime Trilogy features a new title theme instead of the previous Prime title themes. This version features the Title leitmotif with very similar instrumentation and static heard in the first Metroid Prime, plus the addition of heavy drumbeats for dramatic emphasis.
The title theme of Metroid: Other M features the Title leitmotif played on plucked strings over dark ambience. The first few notes of this version can be heard when interacting with the Metroid item in Animal Crossing: New Leaf. It can be heard here:  Another Title remix is heard at the beginning and ending of the credits music: 
While Return of Samus did not feature this leitmotif at all, it was directly incorporated into the remix of that game's own title theme in Metroid: Samus Returns. This version is also heard in many trailers for the game. Another Title remix is heard during the Staff Credit medley, during which the theme is performed by a choir and played alongside Theme of Samus.
- Despite the Title theme being the apparent main theme of the Metroid series, Super Smash Bros. Brawl erroneously refers to Brinstar (Metroid) as the Main Theme.
- ^ Name derived from the respective Title themes of Metroid (in Super Metroid: Sound in Action), Samus Returns (in the internal files), Prime (in Metroid Prime & Fusion Original Soundtracks), Fusion (also in Metroid Prime & Fusion Original Soundtracks), and Hunters (in the BGMSELECTLIST.DAT file), which all prominently feature this theme