(An old exercise, a bit of a third part to the exercises: "Why do theology?" and "What is Theology?")
Theology is important to the Christian for two reasons. It gives our faith substance, and it gives our lifestyle an ethical guide to follow.
Faith by definition needs something to trust. Theology is important because it gives the Christian the focus of faith. To simply say “I trust God,” without an idea of who God is, is not enough. It would be even worse to have a faith placed in the wrong idea of God. If someone decides to place their trust in the Mormon idea of who God and Christ are, they are placing their trust in a false hope. That is not a picture of God as He has revealed Himself to us in scripture.
Some may think that Theology is to “abstract” to reflect their personal experience with God. In reality they need to have a correct understanding of God to discern if their experience was even with Him, and not just something they imagined. They also need to correctly understand how to relate to God and to others in such a way as to please God, or their experience could serve them no good. A personal experience of God without a response of faith placed in Christ is worthless. A correct understanding, however limited it may be, of scripture relating to man, sin, and the atonement, is necessary to benefit from an initial experience with God. Simply put, salvation depends on a correct understanding of scripture.
Once saved, Theology is necessary to live a life pleasing to God. A correct understanding of God, and man as a creation of God, gives rise to a life that is lived as God would desire. Good ethics depend on the truths expressed in scripture, defined by a good Theology.