Some of the poetry of the Machzor thinks that it helps to have the angels on our side.
There is an explicit passage in the Selichot that says, Machnisei rachamim hachnisu rachameinu lif’nei ba’al harachamim – “Angels of mercy, usher in our prayers for mercy before the God of Mercy”.
Written by Rav Amram Ga’on in the 9th century, it reflects a doctrine of angelology that many commentators found too theologically debatable.
Of course it all depends on whether we take the words machnisei rachamim as meaning “angels”. A possible alternative is to see them as a metaphor for the sound waves or thought waves that link mortal Man with the immortal, non-physical Creator.
If we take the words literally as meaning angels we cannot be certain that the angels are on our side.
There is a Talmudic notion (Shab.12b) that the angels do not know (perhaps the Hebrew means “value”) the Aramaic vernacular in which our ancestors expressed themselves at some ancient period, and this may be a warning not to rely on angels.
According to the Midrash (early in B’reshit Rabbah), the angels tried to stop the creation of man because he would be likely to prove unworthy of God’s blessings, so possibly the angels feel threatened if God listens to Man.
But the liturgy insists that He does listen to us and the only thing that can work against us is our own failings.
Even if the angels want to be on our side, we don’t really need them. Thank God we have a direct line of communication On High and we can manage without angelic services.