From what I understand, a battery contains an inherent potential difference from its materials, and when a path is connected, the electrons move. Your picture is misleading, unless I am mistaken. That battery would expend its energy across the electrolyte. A salt bridge needs to seperate the anode/cathode. And then the electrons can be tunnelled through the wire and ending like a dud by putting a measely chloride ion into solution... that's where I believe the electron goes. So, the cathode is rolling out electrons, which get absorbed by the nearest atoms, and an electrical gradient ensues. The negative forces repel electrons at the anode, polarization occurs, and the batteries electrons are forced into the metal ion. This ion follows its original electrons as they conduct into the anode, absorb the battery's electrons, and deposit as a metal. Chlorine gas at the cathode can form because 2 chloride ions got jammed-up with electrons, and found themselves with an extra bond of electrons, which it was glad to force on to the next atom. I could be arse backwards, though, lol, I hope it makes sense. And the salt bridge would force the electron through the wire, ending up inside of a metal atom... and pulling off a positive ion from the salt bridge. Anyways, have fun correcting my mistakes.