This is quite the topic, dear! Indeed, myths are an engrossing and highly fascinating topic of which there is far too much to be said to give even a fair sampling in a single post. However, generally, myths can be found to have their roots in either historical, but romanticized events, or, more commonly in the case of the very ancient myths of antiquity, in the heavens and the drams which unfold upon them. Very commonly, one finds that a cornerstone of a 'myth' is indeed a case of euhemerization of some historical of quasi-historical figure. Such is oft the case especially in the Norse and Greek myths (see Mallet's
Northern Antiquities as well as
Hesiod, and Plato's
Dialogues for further study). A brief example of this is to be found in the
Phaedrus of Plato:
Phaedrus: Tell me, Socrates, isn't it from somewhere near this stretch of the Ilisus that people say Boreas carried Orithyia away?
Socrates: So they say.
Phaedrus: Couldn't this be the very spot? The stream is lovely, pure and clear: just right for girls to be playing nearby.
Socrates: No, it is two or three hundred yards farther downstream, where one crosses to get to the district of Arga. I think there is even an altar to Boreas there.
Phaedrus: I hadn't noticed it. But tell me, Socrates, in the name of Zeus, do you really believe that legend is true?
Socrates: Actually, it would not be out of place for me to reject it, as our intellectuals do. I could then tell a clever story: I could claim that a gust of the North Wind blew her over the rocks where she was playing with Pharmaceia; and once she was killed that way people said she had been carried off by Boreas...
In the ancient Egyptian and Chaldean myths, much the same is to be found. It is also to be noted that many of the familiar myths of classical Antiquity and the early Middle Ages may be found to have certain familiarities with the elder myths from which they doubtless owe at least some of their lineage to. The Greeks themselves we know from the likes of Plotinus and Plato, as well as Pythagoras and so on, were greatly indebted to the hierophants of Egypt, particularly those at Heliopolis, Thebes, and Alexandria. There is also a great deal to be said about the mythic wisdom acquired by many like Pythagoras from journeys into the near East as well as India. See Cory's
Ancient Fragments for some related background on the ancient world.
The import of the zodiacal mysteries and ancient star cults cannot be overstated in regard to the role they played in the development of the familiar myths. Indeed, a quick perusal of classical Greek mythology offers telling insight into the astral mindset of these ancient authors and the creation of the otherwise indecipherable and fantastical myths that many are so familiar with, as they have been preserved and passed down to us from the Romans, through Mother Church and onto a great dispersal under the scatterings of medieval Europe.
For further reference, see:
https://greekgodsandgoddesses.net/myths/constellations/
http://www.inquiriesjournal.com/art...my-as-manifestations-of-ancient-greek-culture
To truly get at the primordial origins of the world's great mythic tradition, coming out of that Cimmerian darkness of the 'antedeluvian' world, it is important to understand fully the implications of this astrological basis of humanity's great many, but ultimately facsimile stories.
The monsters of myth themselves often arise from frightening astronomical or earthy events, such as comets, meteors, eclipses, and a panoply of catastrophic events. In particular, with many of the greatest and more fearsome beasts of mythology, there is an underlying connection to the stars and our zodiacal travels.
Examination of classical astrological charts will give one some insight into such things, as there is a clear, cyclical "war" in the heavens, one which recurs at every season, every year, changing slightly as the earth wobbles through space.
In the case of classical Greek mythology, many of the beasts we meet such as the Minotaur, are essentially representations of the wretched perversions of form arising from the interference of the gods (sidereal archetypal principles) in the material, lower world of man. Often these stories of monsters, across all cultures, are dual purpose and are to teach the masses moralistic or profane lessons about life and how it is to be lived. In this way they are essentially archetypal aphorisms not unlike common fairy tales and proverbs. On an esoteric level, they often contain wisdom for the initiated, primarily about the astral realm and the true meaning of the zodiac and star systems.
Many monsters of mythology also arise as personifications and elementals of the various conditions existing upon this earth. The 'salamander' and fire, is one such example.
There are many of these such cases, and are as varied -- though, on a whole of consistent theme -- as the world's traditions. Commonly, "monsters" are the mythic personages of great dangers and cataclysms, usually with a practical message rolled into their characteristic about said dangers.
Finally, I would add that study and reflection upon Freemasonic, Rosicrucian and Kabbalistic symbolism and historiography would be of great value to those wanting a deeper understanding into the primeval myths of man...