References to John in the Bible paint him as one of Jesus' most beloved and faithful apostles. While he shows some anger early in his apostolic career, he became an elder statesman of the early Christian church.
Before meeting Jesus, John was in the fishing business with his brother James and his friend Peter. According to Acts 4:13, John was not highly educated like other religious men of the time. Even so, he accepted the invitation to become Jesus' disciple.
Early in Jesus' ministry, John showed zeal and passion, although sometimes misplaced. For example, he and James urged Jesus to call down fire upon unwelcoming Samaritans. As a result, they received the nickname Boanerges, meaning "sons of thunder," for their vigor. John also attempted to prevent a man from expelling demons because he was not an apostle, but Jesus corrected John on this matter as well.
John, most likely as a result of accepting correction, became one of Jesus' most trusted apostles. He was one of the three to witness the transfiguration. Many Bible readers interpret John to be the beloved disciple who leaned on Jesus during the Last Supper. John was the last apostle to talk to Jesus before his death.
After Jesus' ascension, John took a major role in spreading the Christian message with Peter. While exiled during old age to Patmos for preaching Christianity, he received the Revelation and put it into writing. Upon release, he wrote his three epistles and his Gospel, which emphasized Jesus' love. He was the only apostle to not suffer martyrdom, dying of old age around 100 A.D.