Robyn talked about this song on the promo record SPECTRE, on which he explains each of the songs on RESPECT:

"I was talking to Julian Cope, who knows about these things. The serpent
generally a symbol of wisdom as much as a symbol of deceit. The serpent
is a symbol of knowledge, I mean, it is the serpent that gives Eve the
apple. The idea in my song is that the serpent is guarding wisdom. He's
guarding it like a kind of reverse Garden of Eden. But the serpent
can't go in, just as I don't know whether the angel that guards the
gates of Eden, and who drove Adam and Eve from the gates, is actually
allowed into Eden himself, or itself, 'cos we don't know what sex angels
are -- hopefully, both. Actually, the idea of a whole load of kind of
she-male angels is fantastic, all sort of standing there. You can
imagine Madonna would suddenly burst out of a cardboard box, lured by
the presence of such androgyny, which has nothing to do with this song.
It's the one on the record I think of as the least 'Robyn Hitchcocky.'
I wrote the song almost as a take-off of The Band. I imagined Rick
Danko doing the lead, and the other two coming in. And in the absence
of The Band, we had to do it ourselves."