The English language lends itself so well to rhyme that rhyme is common in English poetry, except for blank verse which has meter and no rhyme and free verse poetry. But even free verse poets can make use of internal rhyme in which two words within a line rhyme, use approximate rhyme, or the poet can end a free verse poem with a rhyming couplet. Poets have great creative license today in regards to rhyme. And basically there there are two major kinds of rhyme, approximate rhyme in which the end words of a line echo similar sounds and exact rhyme in which the exact sounds are repeated in two different words.
There are many rhyme schemes in found in traditional English poetry. but for the purposes of this article I will give you examples of five common types with probably the most common being alternate rhyme ABAB CDCD EGEG with ballades in particular making use of this device with an ABAB CDCD CDCD scheme.
The people along the sand A
All turn and look one way B
They turn their back on the land A
They look at the sea all day A
As long as it takes to pass C
A ship keeps raising its hull D
The wetter ground as glass C
Reflects a standing gull D
Another really common rhyme scheme is the couplet with an AA BB CC pattern.
Twinkle, twinkle little star A
How I wonder what you are A
Up above the world so high B
Like a diamond in the sky B
Another device is mono rhyme in which each line of the poem rhymes in a AAAA pattern.
Lifting her arms to soap her hair. A
Here pretty breasts respond-and there, A
The movement of that buoyant pair A
Is like a spell to make me swear. A
There are other more complex rhyme schemes that the poet can employ such as enclosed rhyme enclosed rhyme ABBA and the limerick which is AABBA.
The truth about poetry is that poetry is like spoken or literary music, so the sounds in poetry are important, and a good poet must have a real good sense of sound whether or not he writes free verse or traditional. Your poem should sound like a song in the head of your reader. At least this is my opinion.