The 24-year-old joins Liverpool on July 1, having made 225 appearances for Monaco and winning the Ligue 1 title in 2016-17.
Reds boss Klopp has explained the Brazilian's character and footballing ability is what attracted him to the €50 million signing.
“We have signed a fantastic player, but someone who is an equally fantastic person I think,” the manager told Liverpoolfc.com.
“His reputation as a character in the dressing room and his attitude in training has come through from everyone we speak to.
“He has a lovely family also - adding a person like this to our dressing room only makes us even stronger. What we have - in terms of our environment at Melwood and in the team - means anyone coming in must be of that build. They must be the highest quality person and player.
“He has ability and mentality to play at the highest level in a number of positions. He can play ‘6’, ‘8’ and ‘2’. This is cool.
“He is tactically very strong and football smart. I think he improves our squad and there aren’t that many players you can say that about in this moment, because the quality we have already is so high.
“I like that he is young yet experienced also, with a high number of games at a club that compete to win. Also, international caps for Brazil tells you something about him.
“This signing gives us new opportunities and for that I am excited. I’m sure our supporters will make him very welcome and at home at our wonderful club and in our amazing city.”