Weapons

Okay, so this isn't a poem about warfare, but there are weapons all over the place. What's up with that? The entire third stanza is about weapons, and the speaker tosses in another reference to his sword in the final stanza for good measure. To be fair, the poem is kind of about warfare, but not your typical warfare. It's about waging war on an unjust society, and making the New Jerusalem a reality. For that to happen, and for all the "dark Satanic mills" to go away, some fighting is necessary. The fight is a mental fight, a change in perspective more or less, and so the weapons the speaker describes are really symbolic weapons, despite the fact that the speaker does veer towards Braveheart territory from time to time.

• Lines 9-10: The speaker busts out some alliteration and asks for his bow of burning gold and his arrows of desire. The word "burning" makes us think of fire, and foreshadows the speaker's description of the chariot, whereas the bow symbolizes the violence of conflict (ongoing or impending).
• Line 11: The speaker's demands continue, and he now asks for his spear. As with the bow and arrow, the spear too symbolizes violence and destruction. 
• Line 12: The speaker alludes to the fate of Elijah and asks for his chariot of fire. Elijah ascended to Heaven in a chariot of fire, and the allusion is the speaker's way of identifying himself with a biblical prophet who just so happened to call down fire from heaven to destroy his enemies.
• Lines 13-14: The speaker will continue to fight, and his sword will not sleep. "Sleep" is here a metaphor for lack of activity, or something like that, and this is the speaker's way of saying he will continue to fight for the New Jerusalem. It's also clear at this point that all these are weapons aren't real weapons, but metaphors for a process of changing one's ideas and perceptions (this is a "Mental Fight," after all).