The former Borussia Dortmund striker signed for the Hammers this week.
Fullkrug told the club's website: “The manager was a big reason for me making the transfer to West Ham,” said the 31-year-old, who penned a four-year deal with the Hammers earlier this week.
"I have been thinking about West Ham for a long time now. His play-style is important for me, and I need this to bring my best performance on the pitch. He knows that and will try to give me this.
“We have so much quality in this team, and if we work hard, be brave, and be patient, then we will have a very, very nice season and can surprise some other teams and hopefully do better next season and reach some European places in the table.
“I have spoken with him (Lopetegui) already, and I like him a lot. He has a lot of authority and is also a lovely person. He shows a lot of emotions, spoke very honestly to me, and gave me some very good examples on how I could work within the team. After this chat, it was clear I wanted to move to West Ham.
"I am very excited to be here. That is why I love these traditional things at a big Club like West Ham because I want the shirt to be a bit weighted when I wear it, as I like the pressure. The fans want to see a successful team, see a team that gives everything on the pitch, and I hope they will be happy with me as I always give my best.”