Lambert, who says he's been an admirer of his new signing for quite some time, believes El Ahmadi will quicken up the tempo in the middle of the park with his impressive range of passing skills.
He told Villa's website: "Karim is someone I have been aware of for a while. I think he will be great for us. He is a very, very good footballer.
"I don't think he's a set player in terms of defensive or offensive. He can do most things and could do both roles if I asked him to do that.
"Certainly I won't curtail him and will let him play with freedom because I think that is the way he plays. He is a very good player.
"It was pleasing to get the deal done early because we needed someone who can put their foot on the ball and move it about a bit quicker. I think he'll do that for us.
"I think your eye as a manager tells you what a player is like in terms of their good habits and bad habits as well as how well they can move the ball.
"I think he can move the ball well and, at 27-years-old, he's an experienced player who has played international football.
"He's played at top club in Feyenoord and played in some big games in Holland as well."