But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction. 2 Peter 3:1
This passage confirms the existence of two things: "false teachers" and "destructive heresies". That means that not all teachers are teaching the truth, and not everything you hear taught is spiritually sound. Many denominational churches believe that it doesn't matter what you teach or what church you're a part of. They teach that as long as you believe in Christ, differences of doctrine are trivial. If that were true, then there could be no such thing as a false teacher, but Peter clearly taught that false teachers are a real and present danger. In fact, he goes as far as to describe their teaching as "destructive heresies" and warns that such teaching leads to "swift destruction". It's clear that false teaching cannot bring a person nearer to God, but is instead destructive of that relationship. Compare this passage with 2 Timothy 4:3-4...
For the time is coming when people will not endure sound teaching, but having itching ears they will accumulate for themselves teachers to suit their own passions, and will turn away from listening to the truth and wander off into myths.
So teaching can either be sound or it can be false. Sound teaching would reflect truthfully what the bible teaches, without adding to it or taking anything away. Anytime something other than the truth is taught however, it is just a myth. Utterly worthless. Empty. The truth can teach men what God expects of them, which is terribly valuable. A myth simply can't help you spiritually.
So seek after sound teaching, avoid destructive heresies, and study often so you know the difference.