Lees, 22, will join up with Stuart Pearce's squad for a week-long training camp in Turkey ahead of the tournament, which starts on June 5.
"Playing with the U21s broadens your skills and your experience," Lees told the club's official website.
"You know all the players at your club, you know what they do in training, and it's good to go away and mix with different players.
"Training is of a great standard, the manager is great and the squad is really, really strong. The summer squad was tough to get in and it'll be an experience to be involved."
The Leeds academy product, a regular in Pearce's squad during qualifying, added: "I didn't represent England when I was younger.
"I came straight into the Under-21s and maybe you relish the opportunity more because I haven't done it as a young player."
England's opening group game is against Italy on June 5 in Tel Aviv and they play Norway in Petah Tikva on June 8 and hosts Israel in Jerusalem on June 11.