Actually, both free verse and formatted poetry only require that one knows how to speak, though writing ability helps.
  The earliest poem I remember creating was before I could read (or read a clock, for that matter), though I knew some numbers. I looked at a round-faced clock at 9:50 and said,
Ten-ten.
Ten to ten.
This poem incorporates both rhyme (in the form of repetition) and meter (I paused between the two "ten"-s in the first line, so the second line had the same pacing; of course the "ten"-s were the emphasized syllables). I don't say this to play genius, but rather, to show how little ability a formatted poem requires.
  On the other hand, children tend not to learn free verse until they've been writing formatted poetry for quite some time. This is because the patterns in the words are less obvious, although they are there. It takes more skill to recognize them, and likewise, to make them of course.
  Both free verse and formatted poetry have plenty of substance. I find this hard to argue, since it feels so obvious to me, but here it goes...
Both types of poetry have room for poetic devices.
Both types have meaning.
Both types use words in a musical manner.
Have I missed anything?