sorry, i put the wrong poem.

Kissing a Horse, robert wrigley

Of the two spoiled, barn-sour geldings
we owned that year, it was Red—
skittish and prone to explode
even at fourteen years—who'd let me
hold to my face his own: the massive labyrinthine
caverns of the nostrils, the broad plain
up the head to the eyes. He'd let me stroke
his coarse chin whiskers and take
his soft meaty underlip
in my hands, press my man's carnivorous
kiss to his grass-nipping upper half of one, just
so that I could smell
the long way his breath had come from the rain
and the sun, the lungs and the heart,
from a world that meant no harm.

what is the significance of the sun and the rain?

The grass that the horse eats grows because of the rain and sun. It evokes a pure connection with the most basic parts of life.