This is in response to a question on MennoDiscuss: "What is the significance of the letters to the churches in Revelation"
The seven churches represent seven kinds of churches that could exist in any age:
Ephesus-- The doctrinally orthodox church that has lost it's love for the needy
Symrna-- The persecuted church
Pergamum-- The church that upholds the name of Jesus but has compromised its purity from the world
Thyratia-- The church that has been divided by heresy
Also, John intended this section to be a very significant section in his book. One of the purposes of the book, according to chapter one, is that one would be blessed because they "keep the words in this book", in other words, obey it. But the only section that really has stuff to "obey" is the letters section.
Thus, the letters are just as significant as the rest of the book. Sure, 4-20 talks about what happens to those who obey or disobey, but the meat of the book-- what IS the obedience he's talking about-- is found in 2-3.
If we put these churches in a historical box, we will miss the point of what the letters are saying to us.