Guys, I am from South America, Chile
The answers to your questions are, that...you've got Metallica concerts very often, they live there, I bet that you have seen the band many times.
When they come down to southamerica, obviously change the setlist, because they don't come too often here, in fact, their last concert here in Chile was, MAY 14th, 1999...TEN YEARS! I think that's why they create or build a special setlist for us...in 2003 they cancelled the south american leg, so I think they felt in doubt with us hahaha and that's why we are so enthusiastic, with a lot of energy, we sing all the shit, even the riffs, these concerts are like once in a lifetime, instead of you, that Metallica always play in the States.
I was waiting them since 2000, and finally could see them like a week ago, and I don't care what song was gonna play...any song I would enjoy XD
well..except of Blitzkrieg, xD
this is my humble opinion, sorry about my poor english.