Roy Hodgson's men had to settle for second spot in their group following a scoreless draw against Slovakia, having previously struggled going forward in their opening 1-1 draw with Russia.
Lagerback feels England have done well at the finals apart from their finishing and hopes their strikers will let them down versus Iceland, too.
"England have done rather well, except from scoring goals," Lagerback said at a news conference.
"Their performances have been good. But football is about scoring goals. I hope they will keep going like this. We want to keep them quiet even more than the other teams.
"It is always difficult to know what to expect. England will normally have more possession. We will see if we can step up that part of the game. We are hoping for the same sort of result as in previous games. The weather conditions will play a role, too.
"There is no need to keep the players down to earth. They are very strong mentally. They are looking forward to the game. We want to take the next step. I think they will be ready and show what they can do.
"We have practiced penalties a bit. Some were good, others not so much. Like normal really."