Most everything on your truck is powered from the ignition switch, but not the headlights and horn.

Are they working?

If not, try adding a jumper from negative post of battery to any handy spot on the engine block. Still no joy?

Try adding a jumper from positive battery post to starter relay & see what it does.

When I had the same problem & my truck fired right up when I added the jumper from negative post to engine block, i knew the negative cable was shot.