I have a 2004 ford F150 trition 4x4, I bought it in march, i happen to notice that my head lights wouldn't shut off this afternoon after when I got home from town, after several phone calls n different ideas I resorted to removng a battery cable to keep my battery from dying, then tonight I decided to go to my dads, when I put the negative cable back in the battery I noticed it sparked. she drove fine there, got done visiting n on my way home my horn goes off n won't shut off till I stopped n turned the truck off, I drove all the way home with it blowing like crazy, I took the fuse out but my truck will not start with out the fuse!! I have to work tomorrow night n I have no clue what's going on!!

 

My first thoughts are battery and fuse block.
If the battery is old and dying, it can cause some weird electronic malfunctions. Dirty/corroded cables and/or terminals can do the same.
There's a known issue with water leaking on to the back of the fuse block. That can do all kinds of weird things. Pull your door sills up and check for standing water in the wiring channels. Check both sides just to be sure.