Dislocation
A perfect crystal would
shatter when struck. Real metal bends because of a flaw: an
extra half-plane of atoms that ends mid-lattice. Force makes that flaw
glide — one row of bonds breaking at a time — instead of the whole plane snapping at once. That moving fault is a dislocation, and it is why a paperclip folds rather than cracks.
Drag left or right to push the dislocation through the lattice. Watch the slip travel row by row. The arrow is the Burgers vector — the size of the step the crystal takes.