When I write lyrics, the form is relaxed. When I write poems I stick to rhyme, rhythm and metre. Many 'poems', including ones in print, are nothing more than prose with excessive carriage returns.
The most important part for me is rhythm. dum DUM, dum DUM, dum DUM, dum DUM.
Why? Because poems should be read aloud. Here is a sonnet of mine:
The Art of Deception
We talked about the crisis in the arts
Tomfoolery the order of the day
Exhibiting two supermarket carts
No skill with paint or pencil or with clay
I sympathise with those who have a skill
Yet fail to get attention they have earned
And it will be a while for them until
The wheel of style is ready to be turned
Since rubbish is the thing that they expect
We had to follow suit or face neglect
But though we've garnered worldly wealth and fame
Deep down I feel pretentiousness and shame
I laughed so hard I had to dry my eyes
The day that your blank canvas won first prize