Background
"The Tyger" was written by William Blake and first published in the year 1794 as part of the poetry collection book Songs of Experience. The poem is one of his best-known works. Blake’s poetry is highly symbolic, rife with imagery and creativity.

Structure
The poem consists of 24 lines, broken up evenly into six quatrains. Each quatrain is composed of two couplets, meaning each stanza has a unique AABB rhyme scheme (AABB CCDD EEFF, and so on). This lends to quite a lyrical read of the poem. The first and final stanzas are identical save for the change of one word– "could" is replaced with "dare" in the final lines of each stanza.

Analysis
Tyger Tyger, burning bright,
In the forests of the night;

The opening line directly addresses the Tyger (or Tiger). Of course, it is unlikely the speaker means the Tyger is literally burning in a forest at night. The first two lines indicate the Tyger stands out, while also possible referencing the color of a tiger’s coat. When the reader truly visualizes the intensity of the first two lines, the image is quite striking both in beauty and something akin to fear or foreboding.

What immortal hand or eye,
Could frame thy fearful symmetry?

That fear is then moved forward and spoken of in the following two lines. While the tiger may be beautiful and may stand out amongst other creatures and its environment, it is strong and terrifying. The sentiment is so much so that only an "immortal hand" can frame, in other words handle or contain, the "fearful symmetry" of the Tyger. The symmetry can be pointing to the perfect balance of beauty and power, or destruction, the Tyger possesses. It makes sense, then, that the speaker would claim and believe only an "immortal hand", likely the Christian God, can take control of the Tyger.

In what distant deeps or skies.
Burnt the fire of thine eyes?

The second quatrain opens up with the mention of the "deeps" and the "skies", bringing up high and low. The fire of the Tyger’s eyes can be seen and felt everywhere. The burning description reemerges further demonstrating the power of the Tyger and the awe is brings. It is truly a creature that stands out, one that can be pictured in the skies (heaven) or the deeps (hell, or some place just as terrible).

On what wings dare he aspire?
What the hand, dare seize the fire?

Though it is not explicitly clear whom the "he" mentioned in the seventh line of the poem is, the reader can deduce "he" is the creator of the Tyger. Wings are a symbol of flying and soaring so it makes sense the speaker has used them to point out "he" has risen toward his hopes and ambitions. Those hopes and ambitions were not only to create the Tyger but also to "seize the fire." If the Tyger has been depicted as burning, then one can glean the creator is daring to take hold of (seize) the Tyger (the fire).

And what shoulder, & what art,
Could twist the sinews of thy heart?

The third quatrain continues the questioning of the creator and perhaps tamer of the Tyger. The strength, support, and "art" of the creator pulled together the tissues and fibers of the Tyger’s heart, that which beats to make it live.

And when thy heart began to beat,
What dread hand? & what dread feet?

The "dread hand" and "dread feet" can be referring to the hands of the creator and the feet of the Tyger. The creature is swift and strong. The creator with the shrewdness and brawn to "frame" the Tyger has his own dread, as the actual creature does.

What the hammer? what the chain,
In what furnace was thy brain?

These two lines symbolize the physical creation of the Tyger and what guides it, the brain. The brain controls thought and movement and was something which the reader can visualize being forged as a blacksmith makes an object. Once again, the image of burning comes into play where the Tyger is concerned.

What the anvil? what dread grasp,
Dare its deadly terrors clasp!

Once again the word "dread" is used. This is apt considering the Tyger has been painted as something of beauty and terror. However, in these two lines it seems the creator has a "dread grasp" that dares to hold on to the "deadly terrors" of the Tyger.

When the stars threw down their spears
And water’d heaven with their tears:

These lines may be the most difficult to understand literally. The spears of the stars can be taken as the light they give off and the water the heaven shed as tears may symbolize rain. What is of note is how both are celestial, pointing to the Christian God as the creator.

Did he smile his work to see?
Did he who made the Lamb make thee?

Here the speaker is asking if the Tyger’s creator is the same one who created the Lamb. The Lamb is from one of Blake’s other poems and is also a Christian symbol. The Lamb of God is a very well known symbol of Jesus, meaning the speaker is wondering if the same God created both. The speaker of the poem also wonders if the creator, again presumably the Christian God, smiled upon seeing his work of the Tyger completed.

Tyger Tyger burning bright,
In the forests of the night:
What immortal hand or eye,
Dare frame thy fearful symmetry?

As previously mentioned, the final stanza is nearly identical to the first stanza save for the change of a single word– "could" is replaced with "dare." The principal question of who was able to make the creature with a balance of being beautiful and terrifying has now been rephrased to ask how it the creator dared make the Tyger.

Summary
There are many questions posed in the somewhat concise poem by William Blake titled "The Tyger." Many, or most, of the questions center on the origins of the Tyger– whether it be who his creator, how he was made, or why he was made. Throughout the entirety of the poem the reader sees a burning, fiery imagery as related to the creature in question and the symmetry of its beauty and frightfulness is never forgotten.

Theme
Three of the themes in the poem all tie in together: awe, curiosity, and religion. It is not surprising to have many questions about everything in the world, especially a creature that can bring awe by both its beauty and ability to be terrifying. They are all powerful forces, just as the Tyger. Religion comes into play by bringing in the question of creation while pointing to the Christian God, the maker of the Lamb, as the same creator spoken of throughout this poem.

Reference
– http://www.poetryfoundation.org/poem/172943
– http://horan.asu.edu/bookshelf/poetry/blake-tyger.htm
– http://www.britannica.com/biography/William-Blake
– https://neoenglish.wordpress.com/2010/12/16/william-blake%E2%80%99s-symbolism/