My truck will not get no power no lights but my battery is still putting out a lot of juice

I started my truck and then I lost all power
no lights no nothing I turn the key off but the
starter was still trying to turn over like a
dead battery. I took the key out of the
ignition and the battery was still warming up
like it was putting out to somewhere I can't
figure out what's the problem I'm thinking it
might be the computer but I don't know
nothing about electrical