our monthly singing session always has a theme (with the caveat - and as always, the theme is optional so no worries if you have another fantastic song to share, and chorus songs are always appreciated) & I often send out a link from Lyrics.com which is a huge searchable collection of song lyrics and here's a link to songs with "may" in the title with another caveat, some are to the word "may" or the personal name "May" not necessarily the month.