During last year's presidential campaign, he notably engaged in a dispute with Capt. Humayun Khan's Gold Star parents, who spoke out against Trump in a Democratic National Convention speech.
The young boy explained that his mom makes him wear the Marine outfit, causing all of the hosts to laugh, but then said, "I looked just like Christopher, my daddy".
"They shall not grow old as we that are left grow old".
"I will do anything for veterans 364 days out of the year", she said, "but this is the one day that's for the dead".
The president chatted with a woman visiting one of the tombstones.
With their families in attendance, Trump told the stories of three service members killed in the war in Afghanistan, where he said they were fighting "enemies of all civilizations".
This was Trump's first public appearance since returning from a nine-day foreign trip.
Trump also recognized former USA senator and GOP presidential nominee Bob Dole, 93, who suffered lifelong injuries during World War II.More news: McConnell juggling diverse demands on Republican health bill
Kelly's other son, Johnny, is getting ready for his fifth military deployment. The playing of "Taps" echoed as he placed his hand over his heart and military officers saluted.
"As we honor the fearless warriors who gave their lives for ours, spending their last moments on this earth in defense of this country and of its people, words can not measure the depth of their devotion, the purity of their love or the totality of their courage", Trump said.
No matter your politics, if your family has given the most they can for this country, a visit and a hug from the commander in chief is a meaningful act, and a small way to say "thank you".
"The empty chair on a holiday is empty every day", he said.
Trump concluded the events of the day by honoring the "unknown soldiers" represented by the prestigious tomb on the grounds of the national cemetery.
The most recent AP photo of the first lady was taken on May 27 and shows Melania returning home in the early hours of the morning from a nine-day trip overseas with the president.
U.S. Sen. Ted Cruz was among a list of guest speakers addressing hundreds at the Fort Sam Assembly as rain continued to pour Monday morning.
Mattis, who is known as the "Warrior Monk" and is himself known for memorable sayings, borrowed from great figures, including Plato and Supreme Court justices, to pay homage to the men and women who have died protecting the country.