There’s a couple of ways to approach this idea. Literal and figurative.

Within the myth itself, the oldest version has the theft occurring after Zeus banned humanity from having access to fire because of fuckery with sacrifices (that was instigated by Prometheus). So, if taken is the myth is taken literally, it isn’t about whether or not humans could pick up fire that Zeus created via lightning, or other methods, it was about them not being allowed to. By Prometheus giving them fire, he gave them the means to make it themselves rather than it being something the gods owned exclusively.

While that still has the hole that it was basically trying to play games to bypass the command of Zeus rather than giving something humans could have tried to steal on their own, and ignores that fire is a phenomenon of physics and chemistry rather than only being granted by a divine force; it’s still the gist of that original myth as it existed when Hesiod set it down in writing.

Now, I think we all know that the myths weren’t literal at all. There was no Zeus, and lightning wasn’t the only source of fire for humans at all. There’s not much in the way of hard evidence of how humans first harnessed fire, whether it was from external sources like lightning, or lava; or if it was discovered as part of the flint knapping process (little sparks can fly under the right circumstances), or other options.

And it isn’t like the Greeks necessarily held every myth to be literal truth. They did have a degree of awareness of myth as symbolism.

And that’s where the figurative comes in.

If your interpret the myth as fire being symbolic of technology, of thought and philosophy, of shifting from hunter-gatherer culture to a more stable location that allows for development of technology faster, then what Prometheus stole wasn’t fire, it was the essence of divinity, the spark that made the gods other than human.

In that respect, you have to understand that Prometheus wasn’t just some rebellious underling. He was a Titan, descended from the oldest gods, just as Zeus was. He was a god of fire, and in some myths was the one that made humans, shaping us from clay. Which is obviously not unique to Greek mythology, but it sets up Prometheus as not only our creator, but our champion among the gods and titans.

Indeed, he’s credited in myth with bringing us more than fire. Art and science were credited to him as well.

Taken as a story about our place in the world, and how we exist as thinking beings, Prometheus is our drive to understand the world around us, and fire is our harnessing even the most primal of forces to our wit and will. It becomes a story of humanity being more than reactive, animalistic creatures; of us seeking to understand the world around us in a way that no other animal has been seen to attempt.

That fire is the fire of creation, of science, of poetry and dance and song.

And, it’s also possible to interpret the myth in other ways, but there’s a limit to how much is readable on a screen before the eyes and brain nope out, so I’ll leave it at that.

I will add that most libraries will have a copy of Bulfinch’s mythology. It isn’t necessarily a perfect source on Greek myths, but it does a good job at being as complete as possible at the time it was written, and doing so in accessible terms. With it being the default text for a very long time, it’s also ubiquitous. Even if your library doesn’t have a copy, there’s project Gutenberg, and you can find torrents or other file sharing sources for it, for free. Amazon usually has free versions of it available too, though I haven’t looked in a while.