The second concept we learn in I can Only Imagine.

Another important concept we learn in the movie I Can Only Imagine is forgiveness.  This is one of the most important things we can do as a Christian in life.  Jesus died on the cross and forgave us of our sins. 
The leader singer of Mercy Me who was struggling throughout the middle of the movie with forgiving his dad from abusing him in the past.  He was mad at him throughout the movie and harbored this anger and guilt toward him.  It almost felt like he hated his dad.  It took him a while to forgive his dad of his dad's past sins.  He did not really forgive his dad until he remembered what Jesus did for him on the cross. 
During the last half of the movie, the leader singer saw his dad's sickness and his dad was slowly following God.  The lead singer then remembered who Jesus was in his life and the camp experience from the past and how we are supposed to forgive those that wrong us because of what Jesus did on the cross.   He remembered this moment then was able to finally forgive his dad.  At the end of the movie, he forgive his dad and started a new life with him.  He brought his dad to church and his dad's heart changed to the dad he wanted all along. 
Lastly,  it was eye opening to see when he asked his dad for forgiveness and healing his dad changed so dramatically.  His dad encouraged him to follow his dreams.  After that time,  the lead singer started writing and Mercy Me exploded.  This is when his hit song "I Can Only "Imagine" song was released.    This was the first real Christian band that I listened to.