Were glowing like the metal on the edge of a knife..what does that mean?

In Meatloaf’s Paradise by the Dashboard Light what does he mean when he says “were glowing like the metal on the edge of a knife” ?

I believe it’s a ‘simile’ which means whatever that quote is referring to its saying it was maybe a dangerous glow? When you think of knives you think sharp or cut so its probably saying it shining bright compared to the negative item it really is. hope I help a little!
– jo