Part of the quarrels run. The dross picks up 25:4 one chapter later.
Quick answer
Warm words over a cold heart are a cheap pot with a shiny coating. The verse is about a finish that misrepresents what is underneath.
Read both lines
The image is a specific fraud. Common clay, glazed with the waste skimmed off refined silver, so it catches light like the real thing at arm's length. סִיגִים is the same dross 25:4 said to take away from silver in order to get something worth making, and here it has been repurposed as a veneer.
What the verse targets is warmth specifically, not eloquence. Fervent lips are the burning, enthusiastic kind, and enthusiasm reads as sincerity, which is what makes the coating effective. The three verses that follow spell out the same figure at length.
Related: Proverbs 25:4 · Proverbs 26:24 · Proverbs 27:6 · Proverbs 20:15
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.