The 18-year-old striker has taken like a duck to water since being involved with United's senior team wth his performances subsequently leading to a call-up for Roy Hodgson's fine 23-man squad for Euro2016.
West Bromwich Albion's Lambert, who has 11 international caps to his name, feels the teenager is prepared to do a job for the Three Lions in France this summer.
"He is fearless," Lambert told Sky Sports News HQ.
"He has come onto the scene and blown everyone away. I was surprised he was included but full credit to Roy for including him.
"If he gets minutes then I think the fearlessness in him will do well. It's obviously what the country has been asking for for some time now. If you are good enough then you are old enough.
"He has played in some big games this season and he has been the match winner. Roy has looked at that and thought he's ready, even though he hasn't played that many games."