Summing up the plot of Ovid's Metamorphoses is easy. Why? Because it doesn't have one. There you have it, case closed; now go have a snack. What kind of snack did you get? Can we have some? On second thought, you keep it: we're already full of Ovidian goodness.
But how can we be full of the book that has no plot? So glad you asked. The thing is, just because The Metamorphoses doesn't have a recognizable storyline doesn't mean it isn't jam-packed with mythological goodies. (Of course, each of the myths Ovid tells has its own story, but, since there are over 200 of them, we can't really touch on them all here.) In fact, The Metamorphoses is so jam-packed that you don't even have to read it all the way through; if you want a taste of what it's about, you can pretty much start anywhere you want, or just look in the index to find your favorite myths, and go straight to those. In this way, it's sort of like an all-you-can-eat buffet – with the difference that, once you get hooked, you're likely to go ahead and eat the whole thing.
OK, you're saying, but even a buffet doesn't have everything all mixed together: you've got your spring-rolls over here, your rice over there, your salad there; surely there's got to be some sort of organizing principle! Well, you've twisted our arm, and you're right. Here's the breakdown.
Ovid's poem begins with the creation of the world, which he describes in a mixture of scientific and supernatural terms. Then he talks about the creation of human beings, the Four Ages of early humanity (Gold, Silver, Bronze, and Iron), followed by the Great Flood that wiped out all human life except for a Greek guy named Deucalion and his wife Pyrrha. After Deucalion and Pyrrha repopulate the earth, Ovid starts talking about various strange occurrences involving gods, demigods, and mortals, all centering on moments of transformation from one physical state to another. In theory, these stories follow each other in time, though in practice it gets more complicated, as there are lots of flashbacks and flashbacks-within-flashbacks. This sounds confusing, but is actually really cool and fun to read.
In any case, a clearer historical narrative starts to take shape around Book 12, when Ovid starts telling about the Trojan War. (For more information about the Trojan War, check out Shmoop's guides to Homer's the Iliad and Odyssey, as well as Virgil's Aeneid.) Not only does the Trojan War contain the actions of many famous Greek heroes, it also provides the backdrop for the origins of Rome. The origins-of-Rome bit comes in the figure of Aeneas, the Trojan hero whom Ovid follows as he journeys from the ruins of Troy, in modern Turkey, all the way to Italy, where he fights a war and founds a new city (Virgil's Aeneid is all about this). Then, Ovid follows the descendents of Aeneas – i.e., the first Romans – down to what was for him the present day: the age of Augustus, the first Roman Emperor.
Ovid ends the poem with a prayer for the future of Rome and Augustus. He also expresses confidence that he will be remembered forever. In this way, Ovid's poem both stretches back into the distant past and forward into the equally distant future.