I’ve heard a lot of other Christians say that the “third part of the stars of heaven” mentioned in Revelation 12:4 is a reference to the fraction of angels that followed Satan in his rebellion. In other words, this passage tells us one-third of the heavenly host followed Satan. They are the “stars of heaven” mentioned in this verse. Although I am in no position to confirm or refute this, it sounds to me like that interpretation might be a little vague. Is this the correct interpretation? Is Rev. 12:4 telling us the fraction of angels that followed Satan in his rebellion as I often hear, or does it mean something else?
To be honest, it is hard to imagine why it would be important for a Christian to know the exact percentage of the angels who have followed Satan in his rebellion. Our “job” is to love God and live a righteous life and God’s “job” is to protect us from these unseen forces over which we have little if any control.
In any case, this is still a valid question, even if its practical implications are small. The answer is that the Book of Revelation is apocalyptic literature. This was a well-established form of writing in the first century. The rule for interpretation of apocalyptic writing is that, unless the context demands otherwise, all statements are to be interpreted symbolically. This is the exact opposite of historical or narrative style writing, in which the rule of interpretation is to take things literally unless the context demands a symbolical/metaphorical interpretation. For example, when it says that Goliath was 9 feet tall, we assume that he was (approximately) nine feet tall. The number nine (or actually the number six, as in six cubits) is literal, not figurative. However, when it says in Revelation 12:3-4 that “another sign appeared in heaven: an enormous red dragon with seven heads and ten horns and seven crowns on his heads. His tail swept a third of the stars out of the sky and flung them to the earth.” it should be taken figuratively. Is this a literally red dragon with seven literal heads? Did his literal tail literally sweep exactly 33.33% of the stars from the sky? Clearly, this is symbolic. It is about a great spiritual battle in heaven between evil in the form of the beast and the woman, who is a figurative representation of the church (as proved by Revelation 12:17).
Are these stars angels? Possibly, but I doubt it. This is apocalyptic literature. The stars being swept out of the sky represents the intensity of the battle. Are stars always angels? No. For example, in Daniel 12:3 the stars in the heavens are people who will be in heaven. Is there a passage which says that stars are angels? Not that I know of. There is a passage in Isaiah 14:12 in which a fallen star has fallen. Some say that this fallen star is Lucifer/Satan, but it is quite unlikely that this is the correct interpretation because in the context, the fallen star is Babylon. I have not studied this out in detail, but as far as I know, there is literally no biblical precedent for stars being fallen angels. So much for this interpretation.
So, there are many reasons to conclude that Revelation 12:4 is not saying that 1/3 of the angels follow Satan:
1. This is apocalyptic literature, so any numerical statement such as 1/3 should be taken symbolically, not literally.
2. There is no indication whatsoever in the passage that these stars are fallen angels. In fact, if they are fallen at all, they have not fallen until this battle scene takes place.
3. The claim that stars are usually representative of angels or fallen angels is not supported biblically other than a single passage (Isaiah 14:12) which is probably a misinterpretation of that passage.
There are many reasons to believe that the interpretation you heard is not a correct one. Even if it were–even if it were true that 1/3 of the angels follow Satan, it is not clear that this would have any impact on how we live our lives, so this speculation, while interesting, is probably of no practical importance. My apologies if I am coming across too negative here. It can be fun and interesting to ask such questions. However, in doing so, we probably should not take ourselves too seriously.