Jesus confronted demonic powers and delivered people from their influence (Luke 4:31-37, 41). The early church carried on the ministry of Jesus as the apostles focused on these same three areas of ministry (Acts 5:12-16). We should do the same – go about doing good, teaching, healing, and helping people find freedom from the work of the enemy (Mark 16:15-18). The result will be many people being set free and added to the kingdom of God.
I don't believe that Christians can be 'demon possessed', as God owns us. However, demons can influence Christians both externally in the form of various attacks (oppression, affliction, torment, etc) and internally if we give them a 'foothold' through various access points (see Eph.4:26-27).
Paul tells us not to give place to the devil, which means it’s obviously possible. If we give place to the devil, we can give demons the right to 'occupy' parts of our lives (like illegal 'squatters'). At times people have to be loosed or set free from demonic involvement.
We'll discuss this further tomorrow.