I would like to know if Satan is an angel and if so does he work against man? If so, what does the Bible say humans should do to stop him?
Yes, Satan is an angel. He is a cherubim that once covered God with his wings. He sinned because he was proud and desired to replace God. You can read about him and his fall at the following links: Where did Satan come from? and Angels .
His Names – A Clue
God helps us understand what Satan is really like by the names He has given Him in scripture. Satan has many names. His original name appears to be Lucifer or Morning Star. That was a great name. He must have glowed with glory (Isa. 14:12). But after his fall, God referred to him using bad names. Names such as serpent (Gen. 3:1-4 and Rev. 20:2), dragon (Rev. 12:4), devil (Matt. 25:41), and your adversary (1 Pet. 5:8). Revelation 12 gives us all of his names in verse nine.
And the great dragon was thrown down, the serpent of old who is called the devil and Satan, who deceives the whole world; he was thrown down to the earth, and his angels were thrown down with him. (NASB) Rev. 12:9
His names reveal his real character. He strikes at us with surprise and venom – like a snake. He wants to harm us in anyway he can. He will even slander us before God. That is the meaning of Devil – one who accuses. Two different Greek words are used for “adversary” and “Satan.” Each one tells us that he opposes us in a general sense, but the first one suggests that he tries to convince God that those who believe in Jesus Christ do not deserve to be forgiven. Is Satan opposed to those who believe in Jesus?
How To Fight Him
How can we fight him? There are several passages in the Bible that tell us what to do. One of them is found in James.
Submit therefore to God. Resist the devil and he will flee from you. (NASB) James 4:7
This is great encouragement. There are no incantations or some mystical thing to do. God gives us simple practical advice. Resist his temptations. 2 Timothy 2:22 gives us an example when it says,
Flee from youthful lusts, and pursue righteousness, faith, love and peace . . . (NASB) 2 Tim. 2:22
Ephesians 6:10-18 gives us the bigger picture. The passage is often called the “Armor of God.” It tells us how we fight him. A previous question and answer tells us what this armor is.
Satan wants us to either ignore him or become preoccupied with him. If we do not believe that he exists, or we believe that he is unimportant, then he can attack us with deadly surprise like a snake. If we become fearful and preoccupied, then we have taken our eyes off of Jesus. Satan can become our focus. The Armor of God helps us keep our eyes on Jesus while fighting the war. There is our victory. Yes, Satan is an evil angel; and yes we are in a spiritual war (Eph. 6:12), but there is no need to fear defeat.
You are from God, little children, and have overcome them; because greater is He who is in you than he who is in the world. (NASB) 1 John 4:4
The victory is sure because the Holy Spirit is in us.