The thermodynamic observables of the classical one- and two-dimensional
ferromagnetic and antiferromagnetic Ising models on a square lattice are
simulated, especially at the phase transitions (if applicable) using the
classical Monte Carlo algorithm of Metropolis. Finite size effects and
the influence of an external magnetic field are described. The critical
temperature of the 2d ferromagnetic Ising model is obtained using finite
size scaling.