Question

How does the resistance of a metal vary with temperature and why?

Answer 1

Due to increase in temperature, the conductor might undergo thermal expansion which would ultimately increase it's length dimension, and reduce it's area of cross section to keep the volume constant
And these two facts, obviously show that length being directly and area of cross section being inversely proportional to resistance, will absolutely increase the resistance of the conductor metal

Hope this helps you !

Answer 2

because the resistance is directly proportional to the temperature.

the increase in temperature increase the resistance of conductor but it happens opposite in case of semi conductor