As SUN plays a major role in photosynthesis process which fixes the CO2 which we exhale out and provide Oxygen which is very crucial for us to inhaling it.
Also Sun is very much imp for other living org like carnivorous animals,insects, fungi,molds etc.
 There are some bacteria and other organisms that live around hot sulphurous vents at the bottom of the ocean and seem to live without any energy from the sun
Firstly it provides heat energy which is very essential for the recent times this is altered to solar energy.the difference in pressure caused by heat moves the air and produces wind energy.similarly it helps in photosynthesis which gives energy to animals including humans..geothermal energy and hydraulic energy has close relations  with sun.just think about it.hope this helps