Now, current flow is caused by electrons travelling down the wire. At temperatures other than absolute zero, atoms in the wire are in constant motion. Obviously, the motion increases with temperature. Now, these atoms are able to deflect the electrons from their paths and so stop or reduce the current flow. Hence, the electrical resistance increases with temperature because of the reduction in current.
Temperature affects the vibration of atoms and molecules in solids.
In a metal as temperature increases, the vibrations of the atoms increase and this affects the frequency of collisions of the 'free'electrons. These electrons carry electrical current and the collisions are the primary mechanism for electrical resistance. Hence, electrical resistance changes with temperature.