Jon Bon Jovi is finally ready to rock again -- revealing to PEOPLE he's fully recovered four years after undergoing vocal cord surgery and calling the whole experience a "rebirth."

The rock icon opened up about the long road back, admitting that while the surgery was successful, there was a time when his future as a performer was very much up in the air.

Jon says he spent years working with vocal coaches on retraining his voice ... and can now finally say he's back to full strength.

The recovery took far longer than Jon expected, but neither he nor his band ever lost faith the comeback would happen.

In fact, Jon says his bandmates stood by him every step of the way, never looking for other work or talking retirement while he fought to get his voice back.

And now the payoff is here ... with his "Forever" tour set to kick off July 7 at Madison Square Garden.