Paul Tautges gives 6 reasons why you should join one if you are a Christian.

1. You follow the pattern set forth in the New Testament.
2. You have a greater opportunity to use your spiritual gifts.
3. You become a more committed part of a spiritual family.
4. You ensure a balanced Christian life.
5. You avail yourself of the wisdom of the multitude of counselors.
6. You experience the joy of serving others.

Read the whole thing. Also see the free pdf study guide at the end with an extended thought on the topic of membership.

HT: 9marks

You may want to see the way I present 6 reasons that obligate Christians to formally commit to a local church as their privilege.