Joachim Low's squad got together at The Hive, home of Barnet, on Sunday and they appeared relaxed starting their preparations for a second game in four days, having drawn 1-1 with Italy on Friday.
The Arsenal defender's participation had been in some doubt after missing their defeat by Manchester United last weekend and Friday's match through illness.
But Mertesacker revealed he is feeling much better and said there is an even greater personal motivation for him to play well now that he plies his trade in the Premier League.
"For sure now there is an greater incentive to do well," Mertesacker told Sky Sports.
"I certainly know a lot more of the players personally now so that can only be a good thing.
"It's good to be here and it is really exciting for me in particular because it feels a bit like home for me to play here now.
"There is obviously a bit of a rivalry against England. All of us in the squad are aware of that and we are really looking forward to Tuesday."
Low's options for the Wembley date, part of the Football Association's 150th anniversary celebrations, have been hit by injury, most notably to midfielder Sami Khedira who has undergone successful surgery on a torn knee ligament.
Mertesacker's Arsenal team-mate Mesut Ozil and Bayern Munich pair Philipp Lahm and Manuel Neuer will also miss the game.