The subject of a sentence is the thing, creature or person that does the verb in a sentence. Take a look at the following sentence:
The dog chased the cat.
The verb is “chased”. This is the action. But something needs to do the action. That something in this case is the “dog”. “Dog” therefore is the subject of the sentence.
The subject and verb are the fundamental building blocks of a sentence. They are the essential elements to making sure that a sentence makes sense. Without a subject we are lost and the sentence lacks sense. Look at these examples of subject-less sentences:
Chased the cat.
What chased the cat?
Ran through the woods.
What ran through the woods?
Blowing through the trees.
What is blowing through the trees?
Manipulating the Subject
The subject usually comes at the start of the sentence. However, it is possible to create some dramatic effects by putting it at the end. We can see the effect of this in the poem, “The Eagle”, by Tennyson:
He clasps the crag with crooked hands;
Close to the sun in lonely lands,
Ring’d with the azure world, he stands.
The wrinkled sea beneath him crawls;
He watches from his mountain walls,
And like a thunderbolt, he falls.
Look at the last line of the poem. If we were to write this in prose and for the sake of description, we would just say: “He falls like a thunderbolt.”
This is the normal word-order in English:
The subject and verb first: “He falls”.
The adverbial phrase describing how he falls second: “like a thunderbolt”.
Tennyson, however, reverses this order, putting the adverbial first and the subject-verb phrase last. He does this not simply to force the rhyme with “walls” but also to add emphasis and drama to the moment at which the eagle plunges onto his prey.
The method of reversing the normal word-order of a sentence is known as inversion. In rhetoric, poetry and other more literary types of writing it is known as hyperbaton.
You can find lots of other examples here.
Things to do with Language and Literature 