"Let us pledge to make the most of that freedom that they so gallantly and brilliantly fought for and they died to protect", he said.
The son of the retired Marine lieutenant general, Robert, also a Marine, died in 2010 after he stepped on a land mine while on patrol in Afghanistan.
"I especially want to extend our gratitude to Gen. Kelly for joining us today-an incredible man-I always call him general", Trump said.
"While we can not know the extent of your pain, what we do know is that our gratitude to them and to you is boundless and undying-will always be there, Thank you", Trump said.
Among those laid to rest in Section 60 is Robert Kelly, son of Homeland Security Secretary John Kelly.
Following a 149-year-old tradition that dates back to President Ulysses S. Grant, Trump began his first visit to the cemetery as president by laying a wreath at the Tomb of the Unknown Soldier. "We stand in awe of your son and his courageous sacrifice", Trump told David and Rose Byers, the parents. "While we can not know the extent of your pain, what we do know is that our gratitude to them and to you is boundless and undying-will always be there, Thank you", Trump said.
Earlier in the day, the President tweeted a message of remembrance and gratitude to those who have given the ultimate sacrifice.
Secretary Kelly's other son, Johnny, is getting ready for his fifth military deployment. Bob Dole, who suffered permanently crippling injuries as a member of the 10th Mountain Division in a battle with the German army in Italy in World War II. And Kelly's son-in-law Jake is a wounded warrior.
And Trump singled out his homeland security secretary, John Kelly, for whom military sacrifice is close to home.
The President's first Memorial Day address comes as his administration is pushing back against reports his son-in-law and senior advisor, Jared Kushner tried to set up secret communications with Russian Federation.
Trump added: "To the entire Kelly family, today, 300 million American hearts are joined together with you". Elizabeth Dole, and other Gold Star families and service men and women in the audience.
"We only hope that every day we can prove worthy, not only of their sacrifice and service, but of the sacrifice made by the families and loved ones they left behind", Mr. Trump said.
Trump is also set to lay a wreath Monday at the cemetery, the final resting place for many US military members and others who have served the country.
Trump honored Gold Star families calling their fallen loved ones "angels sent to us by God", in his first public address since returning from his first trip overseas as commander-in-chief.