This song is about heartbreak: it’s the song of someone pleading with you to stay, to never leave, to come back. Please don’t break my heart just yet or ever: first tell me you love me for a million years.
This song is sly and funny: it’s the joking ultimatum of someone who doesn’t think you’ll ever dare to leave. It it doesn’t work out after a million years together, then sure, you can say goodbye.
This song is a spell: it’s a trick that a Roman deity plays on an unsuspecting mortal. You agree that yes, you will tell them you love them. Only then do you realize that you are now trapped, for a million years, until the end of your minuscule human lifespan.
But isn’t that what happens every time we fall in love?