Hi there, Estudante.
I wouldn´t say "may" in that sense is old-fashioned, there are words that aren´t much in use outside some settings, or by the average joe. Then from time to time it comes back.
In portuguese "jóia/bacana'' can coexist with "animal" etc, to illustrate the point. To a degree, I mean, whereas ''sacou?" (entendeu?) would be a real outdated word these days.
That´s more; this seems like a band 'with a mind" or perhaps it´s Pete Wentz influence...don´t know for sure, but their second show being at the university speaks volumes! Back here in Brazil we have some singers that are a bit on the intelectual side, Caetano Veloso/Chico Buarque, and song writer turned into writer (Paulo Coelho). So, music goes hand-in-hand with literature, philosophy, and other fields.
Plus, one don´t know if they had some help with writing the song, indeed songs are not so randomly made as we may think, at least sometimes.
Further readings on the band, on Wikipedia.
By the way, "...death do us apart" could be deemed "out-of-date" and even cliché, there are other ways to say that. But there are things that never change!