The Midrash explains that milk symbolizes superior quality, richness of taste, and nourishment. Honey represents sweetness. The goodness of Israel is both nourishing and pleasant.
At some point honey and milk share, a paradoxical quality. Honey is kosher, though it is produced by a non-kosher insect. Milk is kosher, though it comes from a cow whose meat may not be eaten together with milk. ('1' Yalkut Shimoni Proverbs 8:943)