He will join the likes of fellow Lions Johnny Sexton, Mike Phillips and Leigh Halfpenny - who made the switch to European champions Toulon over the summer - in France.
And King, who played alongside Davies in the centres for four years at Scarlets, has tipped him to make a huge impact across the channel.
"Jon will suit the way Clermont play, with their very physical and direct game.
"That's Jon's game, he's so physical and so powerful, it will suit him down to a tee. The fans are really looking forward to having him down there."