The 2D Ising model H = −J Σ s_i s_j − h Σ s_i shows rich metastability below T_c. When the external field h is reversed, the system is trapped in a metastable state; escape occurs via nucleation of a critical droplet of size r* ~ J/h. Watch domain walls form, coarsen, and the system tunnel to the new equilibrium through thermal fluctuations.