This Sunday, in addition to observing the Sixteenth Sunday after Pentecost, we will commemorate the Feast of St. Michael and All Angels. Angels are a curious feature of Holy Scripture and the Church's tradition. The Greek word, angelos, means "messenger;" and indeed, the Bible usually depicts angels as holy couriers, bearing God's messages to humans. Angels are also described as doing God's bidding, such as fighting the Evil One, as St. Michael the Archangel is depicted here in a famous painting by Renaissance master, Guido Reni. But, of course, the angels' primary function, like ours, is to praise and worship God, "Holy, holy, holy Lord. God of power and might. Heaven and earth are full of your glory. Hosanna in the highest!"
Whether you think that angels are flesh-and-blood heavenly beings or simply a metaphor for God's divine communications, angels express human beings' frequent experience of God as distant, inaccessible, and unknowable. Remember, that Moses could not look upon God's face directly, because it would have been too mindblowing to behold, and so could only look upon God's hindquarters, so to speak, as he passed by. Even after that, Moses' face shone with the light of God, which was so overpowering that Moses had to wear a veil whenever he descended the mountain, so that the other Israelites would not be blinded by the light.
In a similar fashion, angels serve as a kind of opaque veil between the unknowable God and our limited human understanding. They represent our need for the message to be tempered in some way, the light dimmed and the content simplified, so that we can process it. That's probably a key reason why God speaks to patriarchs and prophets in their dreams or at night. There are so many more possibilities when we don't limit ourselves to logic and literalisms. Angels and dreams make the barrier between God and humans a bit thinner, so that enough of the light can shine through without blinding us completely.
I think that many of us imagine an embodied, real messenger delivering the divine message, because the messages at times feel so personal to us. Angels transmit not only God's message, but the feeling of God's presence and care. It is as if angels amplify for us the emotional, relational content of God's speaking, not just the words or images themselves. And that gives me a certain joy, knowing that God not only wants me to understand, but to feel in my heart his reaching out to me in love.