The Spaniard has left Real Sociedad after an outstanding season in the Spanish La Liga.
Merino, who won Euro 2024 with his nation this summer, is a combative midfielder who can pick out a pass.
“I think that’s a big part of my game and that shows the character that I have," he said to club media.
"I want to fight for every ball and this is something that I learnt when I was really young. Maybe you can win it, or you won’t. I’m not promising I will win every duel, but what I can promise is that I will fight for every ball with 100 percent.
“It’s always tough to talk about myself in those kinds of terms, but I think I’m a hard worker, I want to call myself a good teammate. I like to work for the team with or without the ball. I’m always thinking about the collective aspect of the game. I like to play with the ball, I have a Spanish culture of football.”