President Obama and Prime Minister David Cameron have joined Year 5 and 6 pupils for a lesson at Mount Pleasant Primary School.
Mr Obama greeted the pupils with "bore da" - "good morning" in Welsh.
Top policeman at Nato Summit says stun grenades were destroyed an hour before they were set to explode in path of world leaders.
'Meet the Forces' day was a crowd puller on Sunday as warships open up their decks in Cardiff Bay following Nato summit.
The day began with a spectacular fly-past over Cardiff and Newport by Nato aircraft.