Will someone please remind me how Skyrim handles this mechanic? Is it essential to have a shield for this? Can't you parry with your weapon or block a punch with your fists?

uesp.net

I read this title of this thread as "Block Party." I thought we were being invited to meet at the Gildergreen Tree in Whiterun for a night of mead and dancing.

You can block with a 2H weapon just fine, but it stops less damage than blocking with a shield. You can block with a one handed weapon but only if it is equipped in the right hand and you have nothing equipped in the left hand. You cannot block with bare fists. If you want to block when punching you need a shield in your left hand. Otherwise, hitting the block button will just throw a left handed punch.