Thrusting from the head of Picasso’s goat are bicycle handlebars. They don’t represent anything, but they are goat’s horns, as night is a black bat, metaphorically.

Come into the garden . . .
. . . the black bat night has flown.

Metaphor, like the night, is an idea in flight; potentially, a story:

There was an old lady who lived in a shoe.
She had so many children she didn’t know what to do.

Here, the metaphorical action is very complicated, especially in the syllables of the second line, bubbling…