The Swede has arrived as Arsenal's senior centre-forward, with Merino having filled in as a makeshift option last season.
The Spain international, on his expectations for Gyokeres, told TNT: "Hopefully loads of goals! That’s what he does.
"He’s an amazing striker. He’s strong, quick, he can threaten in the back of the line as well so that’s the main thing in terms of off the pitch.
"But I’m more surprised about off-the-pitch stuff. He’s a professional guy, really humble and he’s already adapting and ready to learn. He’s always with the eyes open so those are good qualities for a striker to have."
Merino also said: "With every player in the squad, you have to adapt to the principles that the team have already and, at the same time, us as players have to adapt to the team-mate and the qualities and the capacities they have.
"Obviously, Viktor, being such a good striker with his own tools, he’s going to be a massive player for us so we’ll have to adapt to his qualities, try to find him in the right spots.
"And also for him, he’ll have to adapt to our values, to our principles and I’m sure it’s going to be a good relationship there."