Nato delegates have observed an honouring ceremony for military personnel ahead of this afternoon's session.
Wales' First Minister Carwyn Jones stood beside US President Barack Obama, US Secretary of State John Kerry and UK Prime Minister David Cameron.
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.