The resistance of a metal increases with increasing temperature on account of :

The resistance of a conductor increases with an increase in temperature because the thermal velocity of the free electrons increases as the temperature increases. This results in an increase in the number of collisions between the free electrons. 

If we raise the temperature of the metallic conductor, the resistance will increase. What happens in the case of a conductor is that as the temperature rises, the ions within the metal conductor gain energy and begin to oscillate around their mean positions. All of these oscillating ions collide with electrons, causing resistance to increase.