Oh, where to begin. Light is associated with goodness and knowledge. Fire is symbolic of both human progress as well as the dangers of human invention. Er, or possibly the dangers of nature as opposed to humans. You could argue either way.
There’s also the whole Prometheus thing. (The alternative title, remember?) Fire was the one thing that man wasn’t supposed to have because it belonged solely to the Gods. When Prometheus stole fire for man, it meant that man was trespassing on immortal territory. Which was a big no-no and resulted in Prometheus having his liver eaten out every night for the rest of eternity. OK, so Victor didn’t have an organ ripped violently from his lower torso every day. But he did suffer a similar form of prolonged torture (think of all his loved ones being singled out and killed). No, he wasn’t punished for stealing fire, but he was punished for trespassing on immortal territory by playing God.
All right, now we’re rolling. We think the monster quite succinctly summed up the rest when he said something about fire warming you up, but burning you, too. Some things, it seems, bite worse than their bark. Some things (fine, we’re thinking the monster and science in general) can be good or evil, depending on how much care you take in approaching them. And in Victor’s case, that would be no care at all.