Without a doubt, the most important role of Demeter was as a goddess of the Elusinian mystery religion.
Demeter is easily confused with Gaia or Rhea, and with Cybele.
Unfortunately, Demeter was unable to complete the ritual because one night Metanira (the child's mother) walked in and saw her son in the fire and screamed in fright.
Instead of making Demophon immortal, Demeter chose instead to repay her host's generosity by teaching Triptolemus the art of agriculture.
Demeter was literally furious ("Demeter Erinys") at the assault, but washed away her anger in the River Ladon ("Demeter Lousia").
When Demeter and her daughter were together, the earth flourished with vegetation.
Demeter and Kore ("the maiden") are usually invoked as to theo ('"The Two Goddesses"), and they appear in that form in Linear B graffiti at Mycenaean Pylos in pre-classical times.
The Homeric Hymn to Demeter has been dated to sometime around the seventh century B.C.E.
Demeter was revered in Hellenic (and pre-Hellenic) world for teaching mankind the arts of agriculture: sowing seeds, ploughing, harvesting, etc.
According to the Athenian rhetorician Isocrates, the greatest gifts that Demeter gave were cereal, which set humans apart from wild animals, and the mysteries, which give humankind higher hopes in this life and the next.
Demeter herself was central to the older religion of Greece.
The central myth of Demeter, which is at the heart of the Eleusinian Mysteries, is her relationship with Persephone, her daughter through a dalliance with Zeus.
Demeter and Poseidon's names are linked in the earliest scratched notes in Linear B found at Mycenaean Pylos, where they appear as PO-SE-DA-WO-NE and DA-MA-TE in the context of sacralized lot-casting.
Demeter, distraught over the loss of her precious daughter, devoted the entirety of her time and attention to seeking her, which had the consequence of halting the progression of seasons.
Poseidon (his name seems to signify "consort of the distributor") once pursued Demeter, in her archaic form as a mare-goddess.