A poem should be -

stop right there, chum. You’ve hit
the target in four words.

see it there? Like the
Northern Lights, the Aurora Borealis,
like a simile,
flashing through the mind,
reshaping the heavens,

soaring merrily above
should-be-s and shouldn’t-be-s

and - not even like I’ve said.
like nothing else
except itself

poetica my ars

a poet should be
a poem should be.

Michael Shepherd

http://www.poemhunter.com/poem/0287-ars-poetica/