I beg to differ. Each to their own I guess.
Obviously Maiden's songs are often better but Metallica utilizes their catalog quite well in my opinion.
About the setlist rotation:
The encore opener is always either Battery, FFWF, Spit Out the Bone or Blackened. These rotate all the time
10th song of the show is usually something from Kill em all. Most likely Hit the Lights, Whiplash or Motorbreath
The 4th song is likely either something from Black Album or Ride the Lightning(the song). Could also be a random rarity/less played song
The 9th song rotates between Halo on Fire and Sanitarium
The Unforgiven used to rotate with Fade to Black. (Fade was dropped recently so now it's just Unforgiven)
Songs 7 and 11 are a Reload single and Creeping Death. These switch places depending on whether they play Fuel or Memory. They may also play something from Hardwired instead.
These are the main things that came to mind, but it's complicated and there are a lot more.