One of my professors in Seminary rightly observed that pretty much all of the heresies available to the Christian church happened in the first 300 years of the Church. C. S. Lewis pointed out the human capacity to take something good and distort or weaken it into something harmful. Both my professor and C. S. Lewis were mirroring the words of Peter in his second letter about truth and knowledge in the Church. Lewis, Peter and my teacher were all concerned that Christians today have allowed ourselves to be "led away" by false teaching and false representations of the gospel. I could write books on this topic and still not do it justice, but I will concentrate my efforts on three modern paths that lead many Christians out of God's plan and into falseness.
The first modern heresy (I know we hate that word, but it is accurate) is a new wave of Neo-Judaisers. The Judaisers in Scripture would follow the apostles (read about them in Acts an other epistles) and attempt to "clarify" their teachings. The Judaisers would tell their audience that they could continue to follow Christ but that they must hold to Jewish customs (food, festivals, sacrifices, traditions, etc.). Becoming good Jews would solidify their Christian following and walk. The writer of Hebrews and the Apostle Paul firmly and clearly preached and wrote against these false teachers saying that 1) Jesus (not law, tradition, sacrifices) is the one and totally sufficient means of salvation, 2) Jesus plus NOTHING else brings us to the place where we find God's forgiveness, grace, resurrection and eternal life, 3) Jesus is exactly who He said He was ... truth, life, the way.
The second heresy is Neo-Gnosticism. The Gnostics in the early days of the Church said that that there was special and secret knowledge that they and their followers possessed. Peter (Chapter 1) calls their work clever stories and "slanderers of the truth." Many have and continue to seek truth from untested, extra-Biblical sources.
Finally, probably the most prevalent heresy is "The Prosperity Gospel." I don't often quote Ray Stevens, but brother Stevens wrote a song in 1987 called, "Would Jesus Wear a Rolex." It is a somewhat irreverent and funny representation of the television evangelist that asks for money and buys his/her own mega home, jet and all the trimmings of wealth. When people ask me about this I tell them to look at the people in the Bible. How did they live and what did they look like? Only a few prospered materially and all were asked to make heart-wrenching sacrifices.
So ... question of the week ... what does false teaching look like?