A song must move the story ahead. A song must take the place of dialogue. If a song halts the show, pushes it back, stalls it, the audience won't buy it; they'll be unhappy.
“It doesn't bother me to work with so much green screen. I prefer real settings obviously.”
“The poets, therefore, however much they adorned the gods in their poems, and amplified their exploits with the highest praises, yet very frequently confess that all things are held together and governed by one spirit or mind.”