Accepting higher energy configurations
Most accepted changes lead to lower energy configurations, but not all!
Higher energy configurations are accepted, although the probability is lower.
Important because if no higher energy configurations are accepted, the solution may get trapped in a local minimum of energy, unable to reach the global minimum
Probability of reaching any configuration from any other must be > 0
Initial condition is random and it must be able to reach the solution which is unknown, so it must be able to reach every other possible configuration