"Words can not measure the depth of their devotion, the purity of their love or the totality of their courage", Mr. Trump said, calling those who have served in the military "special, special people".
"To every Gold Star family, God is with you, and your loved ones are with Him", Mr. Trump said in a ceremony at Arlington.
Trump specifically recognized General John F. Kelly's son Robert, who was killed in Afghanistan in 2010.
He posted on Twitter: "Thank you, Project Hero, for the new biking jerseys for Karen and me".
On Monday, Trump also made special mention of former Senator Bob Dole of Kansas, who sat in the audience at the ceremony, thanking Dole for his service in the Second World War. In the speech he paid tribute to Army Spc.
Trump also paused to talk to a young boy dressed in a crisp Marine uniform.
The parents of Captain Byers were present at the ceremony. "We will always be there".
From the podium of the cemetery's Memorial Amphitheater, the commander-in-chief relayed stories of those who served and urged Americans to continue with the day's theme of remembrance.
Harris said she knows people are here for different reasons but believes her family is not the only ones thinking of her son.
"They fought and they died in a great and noble act of loyalty and love to their family and to our country", Trump said.
He said multiple family members and friends served in branches across the armed forces. "We do this to remember those who went before", Representative Postles said.
Her father is in the Honor Guard providing funeral honors for fallen service members. We can not repay them. "They were people who made a difference". He sacrificed his life so she could live out the American dream.
Trump finished his first Memorial Day address by honoring the "unknown soldiers" who have lost their lives in service.
Defense Secretary Jim Mattis quoted Robert L. Binyon's poem written during World War 1.