Lucifer is an angel created by God to serve Him.  

Lucifer decided he was not interested in serving God.

Lucifer was jealous of God, he wanted to be equal to God, he was full of pride. 

Lucifer became the ruler or leader of these demons also referred to as evil angels.  Matthew 12:24

So he rebelled and convinced one-third of heaven’s angels to go with him.  

Lucifer was thrown out of heaven to the earth.  Revelation 12:4

Lucifer changed name to Satan meaning adversary.

Satan roams the earth seeking to deceive, kill and destroy all those that oppose him. 1 Peter 5:8