The very name Lucifer is taken from is the word light or luciferous, which means "bringing light" or "illumination." In Satan's case, it is a false light - one that deceives rather than illuminates the Truth.
The reason the enemy appears as an angel of light is because he imitates God. Satan wants us to believe that he is as powerful as God. The Bible does describe him as the "god of this world," and there are millions of people who unknowingly follow him and his leading each and every day.
Paul, however, was intent on bringing true light with the Gospel message. He reminds each one of us that we were once "dead in [our] transgressions and sins, in which [we] used to live when [we] followed the ways of this world and of the ruler of the kingdom of the air, the spirit who is now at work in those who are disobedient" (Ephesians 2:1-2).
However, the fact is that Christ has set us free from the bondage of sin. This does not give us the occasion to boast or to drop our guard. Every gift God gives, Satan counterfeits. Every blessing God provides, Satan seeks to pervert and distort. Every miracle the Lord performs, Satan tries to imitate.
Godly discernment is one of the most powerful tools available to the believer. If you feel as though the enemy is deceiving you, pray and ask God to open your eyes to His Truth.
Prayer: Father, please open my eyes to Your Truth, so I may overcome any areas where the enemy is deceiving me. I pray in the name of Jesus. Amen.
"God placed all things under his feet" (Ephesians 1:22).