Lead, Poe

Alright, listen up, chucklehead. This joke is playing on the fact that lead is a heavy metal, and Edgar Allan Poe was a writer. The joke suggests that someone's mom is a "lead", meaning she is a main character, in a story written by "Poe". So it's a play on words, that might also be offensive, because it could mean that she is heavy. Get it? Probably not, you are dumb.