An angel told me
Shalom and thank you for your question! You would like to understand the purpose of angels, since as you correctly point out, 'G-d is omnipotent and his word is reality.'
The Holy One Blessed be He created – and constantly recreates (if G-d would cease for one moment to will creation into being, it would disappear) the world in a manner of processes. The process of creation is an ongoing emanation of G-dly energy which flows from one supernal world to the next, until it constricts so to speak, into the physical world we know and perceive. All these worlds are also creations of G-d.
You could also ask why the world was created in ten utterances rather than one? The tractate Ethics of the Fathers or Pirkei Avot 5:1 says: "In ten utterances the world was created, and what does this teach us? It could have been created with one utterance (or just 'willed' into being)…" and the mishnah goes on to explain that this was in order to exact payment from the wicked and increase reward for the righteous. There is much to say about what is considered wicked or righteous, but the point here is that Chassidic teaching examines this mishnah in Pirkei Avot and answers many questions that come up. Why for example, does the mishnah talk about punishment of the wicked before reward of the righteous? Why is the term payment used?
First let's look at the first question – why ten utterances and not one? If G-d would have created the world with one utterance, His unity, (the same unity we declare when we recite the 'Shema' prayer – a key prayer and concept in Judaism – countless Jews have sacrificed their lives with it on their lips) would have been obvious and manifest. G-d chooses to hide Himself in a world of multiplicity and division, and desires that we seek Him out and reveal His unity.
The righteous – in this context – are those who are able to serve G-d in a manner that rises above the challenges of the surroundings, they do not have to descend. The wicked in this context, are those who can become tempted to stray, and thus end up in unholy places and situations where the righteous do not tread. This is what G-d desires, because when these people stray, they seek to rise up and overcome the challenges. When they do that, they are revealing the unity of G-d! Thus the mishnah speaks about 'payment' of the wicked. They incur 'debt', but 'pay it back' by rectifying their actions and thus revealing G-d's unity, since they have ventured into areas which need to be elevated and rectified.
What does this have to do with angels? Angels are spiritual beings that serve G-d and their place is in the spiritual worlds (as explained in Kabbalistic teaching) of Creation, Formation, and Action. The meaning of the Hebrew word for angel – Malach – is Shaliach – an emissary. Their task is to transfer spiritual abundance in the worlds and they have specific missions.
The supernal worlds of Emanation and the worlds that are above it, are united with G-d to the point that they are not really worlds, since in the lower worlds of Creation Formation and Action there is multiplicity and division, as I mentioned above. The angels were formed from the supernal lights that fell in what is Kabbalistically called the 'Shattering of the Vessels' which occurred when in the original act of creation G-d constricted His light, in a manner of speaking, in order to 'make way' for the existence of physicality. Their source is in the world of Tohu (Chaos) which is a very high spiritual place but in this world of Action the lights of Tohu need to be contained in the vessels of Tikun – rectification.
Angels, like every other detail of creation, are parts of the fascinating and intricate design of the world that G-d creates in order to help bring it to the state of rectification where G-d's unity will ultimately be revealed, which will take place in the true and complete Redemption, may it be soon!