Sword of Gryffindor
The Sword of Gryffindor is a symbol that represents true courage and bravery, the traits of the house. It is also an allegory, appearing when a true Gryffindor is in need. Harry pulled in from the sorting hat in the Chamber of Secrets and Neville pulls it out in the Deathly Hallows. This proved that the sorting hat had not made a mistake by placing Neville in Gryffindor.
Golden Snitch
First, the Golden Snitch is a symbol for everything that Harry loves and desires. Mainly a normal life and Quidditch. Second, it has the metaphor, "I open at the close" written on it. Harry does not understand this two-fold metaphor initially. He unravels the first part of the metaphor while camping with Hermione, while they are without Ron. Harry remember he almost swallowed this Snitch (from his first game) and puts it in his mouth. The Snitch opens revealing a small stone. Hermione recognizes it as the Resurrection Stone.
Later, when Harry heads off alone to face Voldemort he is holding the stone and remembers the metaphor. He turns the stone and says, "I am ready to die." His parents, Sirius, Lupin and Tonks appear to walk with him to his death.
Ministry of Magic
First, the Ministry of Magic is a symbol of government. In the Deathly Hallows it has been corrupted. The bureaucratization of the Ministry of Magic and the extreme oppressive measures taken is an allegory criticizing the state. The measures include: making attending Horwartd mandatory and forcing all Muggle-Borns to register with the Ministry of Magic.
Race Conflict
The issue pure-blood witches and wizards have with muggle-born witches and wizards can be a metaphor for the issues the Nazi had with Jewish people. In the Deathly Hallows similar measures are taken to control and eliminate muggle-borns and muggles. Muggle-borns are forced to register with the Ministry of Magic, much like Jews begin forced to identify themselves. Their property is confiscated, like the Jews, and many disappear. They are seen as inferior by some pure-bloods because of their non-magical lineage, similar to the way the Nazis viewed the Jews as inferior.
