The problem I'm having with the idea of unusual-subject songs is that anything not in some way about cishet romance stuff is already unusual. (I really really wish I were exaggerating.) So, litmus test time! ("Video" means a link to the song, not always an actual video.)
no subject
"Miner's Refrain", Gillian Welch, about miners. [Video.]
"Barbie Girl", Aqua, about being a Barbie doll and living in a Barbie universe. [Video.]
"The Coming", Arsenal & Gabriel Rios, about... I really have no idea, but I love it. [Video.]
"Shinda Shima, Mellow, about... travel? [Video.]
Oh god, you didn't set prog rock off-limits. Dude.
"Die Eier von Satan, by Tool, ABOUT COOKIES, done in electronic German-rally style. [Video.]
"In The Court Of The Crimson King", King Crimson, I'm not paid enough to determine what prog pieces are about. [Video.]
"Pigs", Pink Floyd, uh... corporate greed, I believe. [Video.]
And then the really out-there shit.
"Butter", by Hot Butter.
"Focus", by Hocus Pocus.
So what's closest?