Your little one has good idea about rhyming words by listening to nursery rhymes, songs and reading books having rhyming words. Above all, he loves to hear these words. He is able to match rhyming words. He may not recognize written words, but looks at the pictures and listens to the words and their sounds to find words that rhyme. Get him to pick the picture cards that rhyme together. The picture card which has both the pictures and the word can be hooked together on a metal ring. For instance, bat, rat, fat, mat, cat all in a group.
What you need to know
The more exposure your little one gets to hear rhyming words, the better. Make it fun. Play games like rhyming basket(objects are placed in a basket), rhyming charts, rhyming rings, etc.