A stainless steel backsplash has to be cut right to start with.
Then you apply adhesive, PL Premium, to the wall, not the metal. Why? So that you don't butter up the counter and the faucet on the way to the wall.
It must be held in place by screws or supports or it will just slide down the wall, it won't stay up like tiles.
Notice the little trick in the corner where two pieces meet. One piece goes straight into the corner. The other piece has a bent lip that will overlap the first one, hiding any problems in the corner.