I'm the walking dead
But I'm just a talking head, a zombie floating

from Eminem – Rap God Lyrics on Rap Genius

Meaning

Just like a zombie, Eminem’s music won’t die. He’s immortal (being a “Rap God”), and has a cemented legacy in hip-hop.

The Walking Dead is a graphic novel and TV show about a zombie apocalypse:

He also namedrops Talking Heads, a seminal new wave band from the 70s/80s. Their bassist explains the origins of their name:

A friend had found the name in the TV Guide, which explained the term used by TV studios to describe a head-and-shoulder shot of a person talking as ‘all content, no action.’
– Tina Weymouth

Fun fact 1: both Marvel and DC have characters that are just floating heads.

Fun fact 2: Even more relevantly, the Walking Dead has floating heads, too (in water).

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