Medievalist wrote that iambic pentameter is the most common meter in English. It is, by far - let's look at some very different things done with it:
The first stanza of Keats' Ode on a Grecian Urn:
Thou still unravished bride of quietness,
Thou foster-child of silence and slow time,
Sylvan historian, who canst thus express
A flowery tale more sweetly than our rhyme:
What leaf-fringed legend haunts about thy shape
Of deities or mortals, or of both,
In Tempe or the dales of Arcady?
What men or gods are these? What maidens loth?
What mad pursuit? What struggle to escape?
What pipes and timbrels? What wild ecstasy?
Three stanzas of Dylan Thomas:
Do not go gentle into that good night,
Old age should burn and rave at close of day;
Rage, rage against the dying of the light.
Though wise men at their end know dark is right,
Because their words had forked no lightning they
Do not go gentle into that good night.
Good men, the last wave by, crying how bright
Their frail deeds might have danced in a green bay,
Rage, rage against the dying of the light.
I haven't marked the meter here bcause I'm lazy and I hope you can see it by now. These are very different moods, and in fact different forms. Keats' piece is an ode: a form that includes a wide variety of variants and in fact encompasses several other forms, but every line rhymes with at least one other rhyme (if you give Keats a pass on Arkady / ecstasy) and each stanza is the same length. Also, I may be wrong here, but I think odes are generally to or in honor of a particular thing or person, as with this one or Keats' Ode to a Nightingale. This particular ode is very calm - in fact I found myself reciting the first few lines to myself, over and over, as I wandered around the quiet and ruined Acropolis. Somewhat ravished it may be, but "silence and slow time" suit it perfectly.
Dylan Thomas's poem has nothing in common with Keats' ode except the meter and a rigid rhyme scheme. It rages, as the words say, It is probably the most famous vilanelle in the English language; I've included three stanzas here so that you can see how the first and third lines in the first stanza are reused alternately as the final line of each following stanza.
But still:
Thou STILL/ unRAV/ished BRIDE/ of QUI/etNESS,/
Do NOT/ go GEN/tle IN/to THAT/ good NIGHT,/
Don't ever make the mistake of thinking a fixed rhyme and meter limit what you can say or the moods you can convey. It's juggling: you have to get the meter and the sense bot exactly right despite sometimes-conflicting demands. But in my opinion, when you do get it right you have something powerful enough to explode your reader's mind. I'll let Keats have the last word:
Then felt I like some watcher of the skies
When a new planet swims into his ken;
Or like stout Cortez, when with eagle eyes
He star'd at the Pacific - and all his men
Look'd at each other with a wild surmise -
Silent, upon a peak in Darien.