Since you're baton passing a speed boost to Metagross, Hammer Arm is not optimum because of the speed drop you receive from it.
Metagross is also resistant to nearly all priority moves (Mach Punch being the exception), so I think Bullet Punch is redundant when you have Meteor Mash. Earthquake is also needed to deal with other steel types and threats like Terrakion.
I would replace Hammer Arm with Ice Punch to deal with Gliscor and Landorus. Skarmory does wall Metagross without Thunder Punch, but it's not a threat like Gliscor and Landorus.
Ferrothorn can stall you, but as long as you have some boost from Ninjask, you should do okay with Earthquake (which won't activate Iron Barbs).