when i turn my key to start my car i lose all power to my car i checked my battery cable but they look fine to me? any thoughts?

 

Un-bolt them and pull back the rubber covering and look . If green clean with a small wire brush . Also some time the ground at the block can be bad . One time I had a newer battery go out on me like a light bulb ? I was checking every thing . And I was not able to jump start it . Changed the battery car started right up ? And the head lights would light with that battery .

 

Could also be the alternator went out...Before you go to start your car will the dome light come on? bright or real dim? also when u start does it make a clicking kinda noise?