Bowser isn't the first beloved Nintendo villain, to get his own song! For those of you who remember the old cartoon Captain N The Game Master, Mother Brain was voiced by the late singer Levi Stubbs, who also voiced Audrey II in Little Shop of Horrors - so, the inevitable occurred a few years ago! There are two such videos, so enjoy:
https://www.youtube.com/watch?v=53xQq7kiFI8
https://www.youtube.com/watch?v=CDVGwkUcU9s
So if there is to be a Metroid movie, then I hope whoever voices Mother Brain does a cover of the song, whether in the movie and/or for the end credits! They'll have to change some of the lyrics, to fit the theme of the movie - and I actually have one idea in mind, myself 0:-)
And as a bonus, here's a Little Shop of Horrors clip, remade with a conversation between Mother Brain and the Eggplant Wizard (from Kid Icarus): https://www.youtube.com/watch?v=xb5mV_r_x28