There got to be enough of these to put them on their own page. Two new ones added: the filk "Magneto" by Dannell Lites, and the poem "Sister de la Joya and the Beast" by Dimira Marka.
A filk song is an original, often humorous, lyric to an established song. (At least that's the definition I'm using on this page. By some definitions, any sf/fantasy/media-based song is a filk, but here, if the tune is original I'm calling it a song.)
The Bucket Song: By Jaelle and Orla: Parody of "There's A Hole In My Bucket."
Hello: By Dannell Lites. Magneto, to HYDRA.
National Mutanthood Week: By Dannell Lites. Parody of Tom Lehrer's "National Brotherhood Week".
Magda, Aleytys and 'Belle: By Dannell Lites. Parody of Tom Lehrer's "Alma".
Lee: By Dannell Lites. Magneto, to Lee Forrester.
Whatever Became of Joseph?: By Dannell Lites. Parody of Tom Lehrer's "Whatever Became of Hubert?".
The Acolytes' Song: By Dannell Lites. Based on Rudyard Kipling's "Song of the Men's Side."
Mutants: By Dannell Lites. Parody of Tom Lehrer's "Pollution."
Magneto: By Dannell Lites. Another Kipling. This has Magneto dead and facing the afterlife.
Magneto, My First Love: By Tilman Stieve. Parody of "Leader of the Pack."
Magneto!: By Andrew Strassman. Parody of the Pokemon theme song.
Magneto Rules The Isle of Genosha: By Michele Craighead. Parody of "Istanbul, Not Constantinople."
I'm classifying "songs" as original lyrics with original tunes. Note that the tunes themselves are not stored here, because I haven't yet gotten around to getting recordings of them to Jaya Mitai to be arranged. :-)
Lament for a Mutant: By Alara Rogers. A mutant's particularly dark perspective on Magneto.
Angel With A Sword of Lightning: By Alara Rogers. Magneto, circa UXM #150-188. I wrote this ages ago, so forgive me if it sucks. :-)
How Did Magneto Knock Up Rogue?: By Abyss. A silly post from racmx. The Chef from South Park explains the existence of Baby Charles, musically. Humor. (I assume Abyss has a tune in mind for this, but I don't know it.)
Poems don't need to have any tune composed for them at all.
Magda: By Dyce of Destiny. Magneto, about Magda.
Sister Maria de la Joya and the Beast: by Dimira Marka. A poem about Joseph, from the POV of the nun who rescued him.