ANDREWS AIR FORCE BASE, Md.
"In this time of war, we pay special tribute to the thousands of Americans who have given their lives during the wars in Afghanistan and Iraq and who have earned their place among the greatest of generations," Obama said in the Monday evening speech.
Vice President Joe Biden earlier made the more traditional appearance at Arlington National Cemetery on Obama's behalf, saying the country has "a sacred obligation" to make sure its servicemen and women are the best equipped and best-supported troops in the world.
"As a nation, we pause to remember them," Biden said. "They gave their lives fulfilling their oath to this nation and to us."
Obama had readied a similar message of gratitude for his appearance at the Abraham Lincoln National Cemetery in Elwood, Ill., and actually had taken the podium to give the address when the skies opened up with a downpour and thunder, lightning and high winds.
Under the cover of a large umbrella, Obama told thousands gathered that "a little bit of rain doesn't hurt anybody, but we don't want anybody being struck by lightning." He asked people to return to their cars for their safety, and he retreated briefly to an administration building on the cemetery's grounds. A few minutes later Obama boarded a pair of buses to greet military families that came for the event.
Before the storm hit, and in advance of his appearance at the podium, Obama had visited a section of headstones where two Marines awaited him. After laying a wreath, he bowed his head in a moment of silence, his hands tightly clasped. Then a lone bugler played taps.
After leaving the cemetery, Obama met privately with families of veterans and service members currently living at the Fisher House in Hines, Ill. It serves as a home away from home for family members whose loved ones are getting treatment at the Veterans Affairs hospital in Hines, which is about 12 miles west of downtown Chicago.
At Arlington, Biden carried out the traditional wreath-laying at the Tomb of the Unknowns under a brilliant sunshine.
The vice president, accompanied by Adm. Mike Mullen, chairman of the military's Joint Chiefs of Staff, said the country's service members are "the heart and soul and, I would say, spine of this nation." He said taking part in the annual ceremony was "the greatest honor of my public life."
Obama's decision to appear in Illinois, rather than at the national burial grounds at Arlington, had been controversial, and some veterans groups criticized him for it, although he was not the first president to bypass the annual outing.
Paul Rieckhoff, founder and executive director of the group Iraq and Afghanistan Veterans of America, said Arlington is the focal point of the nation's and military's attention on Memorial Day. "When he's not here, it doesn't look like he's on the same page," Rieckhoff said.
Rieckhoff said U.S. service men and women need Obama to use the bully pulpit to remind people that the holiday is not about going to the beach or barbecuing.
"We appreciate that the vice president is going to be here, but it's not the same," Rieckhoff said.
Jay Agg, a spokesman for the veterans group AMVETS, said the annual ceremony at Arlington is "the ideal place for the president to observe Memorial Day. However, his choice to honor our fallen at another national cemetery as other presidents have done is entirely appropriate."
In an e-mail, Agg accused some people of using the day "as an opportunity to score cheap political points on the backs of our veterans and in doing so dishonor them and distract from the true meaning and purpose of Memorial Day."
Associated Press writer Ann Sanner in Washington contributed to this report.