What did Jesus mean when he called James and John "Sons of Thunder"?
Answer from Pastor Bob:
Mark 3:17 says that when Jesus chose the twelve disciples, he chose two hot-heads named James and John, whom he nicknamed the “Sons of Thunder.”
According to Mark 9:49, John stopped a man who was driving out demons because "he is not one of us."
So basically, James and John were way too outspoken and opinionated. Jesus had to teach them to adjust their attitude and learn a spirit of humility and cooperation.