What metaphors are used in A Storm of Swords by George R.R. Martin?

The wall is a metaphor for isolation. The Wall is a large wall in the north that divides the civilized lands from the wild north and the wilding lands. The Night's Watch is in charge of guarding the Wall. After the Others attack the Night's Watch at Fist of the First Men, the Watch flees back past the Wall. The wildings scale the Wall to invade the Seven Kingdoms.