Could a minister whose message doesn't line up with God's Word be a minister of Satan?
Yes, Scripture warns that if a minister's message does not line up with God's Word, that person could very well be a minister of Satan, who is the angel of light. They are transformed as ministers of righteousness, but their end is according to their works.
Les teaches that we must be careful to examine what we see and hear and ask whether it lines up with the Word of God. If it does not, he says he would very cautiously say that such a person could very well be a minister of Satan, who is the angel of light. Earlier in the same passage, Scripture describes these ministers as transformed as ministers of righteousness, seemingly shining like an angel of light and appearing to have power, yet their end is according to their works. Les also relates a Bible scholar from England who envisioned such people standing before the great white throne, a place only for the lost, suddenly realizing their faith wasn't what they thought it was. So the test is whether the message aligns with God's Word.