Hesiod's Theogony is a large-scale synthesis of a vast variety of local Greek traditions concerning the gods, organized as a narrative that tells how they came to be and how they established permanent control over the cosmos. It is the first Greek mythical cosmogony.
The initial state of the universe is chaos - a dark, indefinite void considered a divine primordial condition from which everything else appeared. Theogonies are a part of Greek mythology which embodies the desire to articulate reality as a whole; this universalizing impulse was fundamental for the first later projects of speculative theorizing.
In many cultures, narratives about the origin of the cosmos and about the gods that shaped it are a way for society to reaffirm its native cultural traditions. Specifically, theogonies tend to affirm kingship as the natural embodiment of society. What makes the Theogony of Hesiod unique is that it affirms no historical royal line. Such a gesture would have sited the Theogony in one time and place. Rather, the Theogony affirms the kingship of the god Zeus over all the other gods and over the whole Cosmos.
Further, in the "Kings and Singers" passage (80–103), Hesiod appropriates to himself the authority usually reserved to sacred kingship. The poet declares that it is he, where we might have expected some king instead, upon whom the muses have bestowed the two gifts of a scepter and an authoritative voice (Hesiod, Theogony 30-3), which are the visible signs of kingship. It is not that this gesture is meant to make Hesiod a king. Rather, the point is that the authority of kingship now belongs to the poetic voice - the voice that is declaiming the Theogony.