OK, first things first I'll eat your brains
Zombies love to eat the brains (Monster reference)
Another interpretation is that Nicki’s going to take all your knowledge (eat/pick your brain) about conquering the music industry, as she declared in the previous line. The your could be referring to Jay-Z or Kanye who are two of the biggest moguls in hip-hop with the most knowledge to consume.
To help improve the meaning of these lyrics, visit "Monster" by Kanye West (Ft. Bon Iver, Jay Z, Nicki Minaj & Rick Ross) Lyrics and leave a comment on the lyrics box