Reductions with metals

As you probably know a good way to reduce some functional group is to dissolve a metal into a solution of HCl, NH3, and so on. This class of reduction is known as dissolving metal reduction. Infact there are different metals which at a low oxidating state (ex Zn(0), Li(0)) readily give their electrons. 

1. The initial process is an electron transfer which results into the formation of a radical anion
2. The radical anion may protonate if a proton source is avaiable (ex HCl, NH3 and so on) or the molecule can fragment if there is any suitable leaving group. 
3. The radical can be reduced and protonate