Yes we have free will, we can choose to follow God or not.
"Now there was a day when the sones of God came to present themselves before the LORD, and Satan also came among them. And the LORD said to Satan, 'From where do you come?'
So Satan answered the LORD and said, 'From going to and fro on the earth, and from walking back and forth on it'.
The the LORD said to Satan, 'Have you considered My servant Job, that there is none like him on the earth, a blameless and up right man, one who fears God and shuns evil?'
So Satan answered the LORD and said, 'Does Job fear God for nothing? Have You not made a hedge around him, around his household, and around all that he has on every side? You have blessed the work of his hands, and his possessions have increased in the land, But now, stretch out Your hand and touch all that he has, and he will sureley curse You to Your face!'
And the LORD said to Satan, 'Behold, all that he has is in your power; only do not lay a hand on his person.'
So Satan went out from the presence of the LORD."
Job 1:6-12
From this quote I find that Satan does walk the earth, is an actual being not just an evil force, and does try to influence our lives. If we think any less of him we are underestimating the adversary.
Now why would Satan do something like this, take a man that is in a close and right relationship with God and try to pull him away. The answer is simple, because Satan hates God. Satan still holds a grudge for getting kicked out of Heaven. Satan is trying to hurt God by taking his children away.
By Satan walking to and fro on the earth he has spread his influence, hence creating the vast amount of misery, hurt, appaling acts of humanity. Why is this important? Has anyone ever heard someone say "If there was a God why would He let this happen?"
The answer is two fold. One because Satan has influence on earth and will do everything he can to make someone think that God is useless and does not care about them. Two because that person has not accepted Jesus/God into their life and asked God for help. Please take note that Satan had to ask God to let Satan make Job's life a living hell before he could do anything against Job. Please also take note that Satan had to leave the Lord's presence before assaulting Job.
Satan will not always try to make us suffer to think God does not love us. He will tempt us like he did Jesus. To try to faulter in our convcitions and pull us away from God. How many of you have heard a parent tell their child not to take candy from a stranger. Satan is like that stranger, wanting to kidnap us a keep us away from God.
Sorry if I rambled; In conclusion Satan is a real being and his objective on earth is to keep us from God.