William Shakespeare wrote Sonnet LV following the form of the English sonnet.  This type of sonnet has fourteen lines with three quatrains and a terminal couplet.  This sonnet is one of several poems dedicated to a young English Lord. The tone of the poem is loving, despite the reference to war.  Its purpose is to ascribe immortality to the subject of the poem.

In essence, the poem discusses time and the power of poetry.  No monument will outlive this poem.  But the young man  will stand out even more than the verse.  His excellence will outlast the dusty gravestones which have been damaged by time.  

When war has ruined statues and broken the mason’s bricks, the man and this poem will live on.

When wasteful war shall statues overturn,
And broils root out the work of masonry....

War personified shall not circumvent these words about his memory.  Future generations will praise him even unto the end of time when the Lord will arise from his grave on Judgement day. 

Personification is a figure of speech in which an inanimate object or abstraction is endowed with human qualities or abilities. In this poem, personification is used when referencing the marble monuments' capacity to have life. 

Not marble, nor the gilded monuments
Of princes, shall outlive this powerful rhyme;