What does Matthew 24:27 mean?

Nobody will miss the return of Jesus. The event won't be exclusive, or hidden, or known only to a few. When He comes the next time (Revelation 19:11–15). At His second coming, He won't appear only to a small group of the faithful. He won't be hidden away in the "inner rooms" of some monastery-style retreat. He won't be off in the wilderness with news arriving to them as a rumor (Matthew 24:25–26).

Here, Jesus adds more dramatic emphasis to this point. His arrival will be as public, and as obvious, as a blast of lightning. He ties this to His role as the "Son of Man," a title also taken from prophecy (Daniel 7:13, Matthew 26:64). While Jesus' first coming was in humility (Luke 2:7), and for sacrifice (Philippians 2:8), His second coming will be in His absolute power, and for judgment (Hebrews 9:27–28; Romans 14:11).

Jesus doesn't want His followers to be led astray by false saviors: those trying to deceive Christians by distorting the truth He has taught them. He doesn't want them led into doubt, unbelief, lawlessness, or lovelessness (Matthew 24:10–14).