President Reagan, standing amid the temple-like, marble columns of the Memorial Amphitheater at Arlington National Cemetery, recalled the victims of the Vietnam War and the space shuttle Challenger yesterday in a Memorial Day address laced with the theme of peace through strength.

"Today is the day we put aside to remember fallen heroes, and to pray that no heroes will ever have to die for us again," Reagan told the sun-bleached crowd of veterans in full-dress, solemn relatives of deceased veterans, and restless children, too young to remember a time when the nation was at war.

" . . . We owe a promise to look at the world with a steady gaze, and perhaps a resigned toughness, knowing that we have adversaries in the world and challenges, and that the only way to meet them and maintain the peace is by staying strong," Reagan said. In a passage directed at Vietnam veterans, the president said, " . . . We must be strong enough to create peace where it does not exist, and be strong enough to protect it where it does. That's the lesson of this century, and I think of this day."

Reagan's brief address drew sustained applause from the audience of approximately 6,000, and seemed to please representatives of several dozen veterans groups.

"I'm from the old school, and I like to see it done right," said World War II veteran Hugh Seckinger, of yesterday's ceremony, in which the mournfulness of a wreath-laying at the Tomb of the Unknowns mixed with the pomp of the U.S. Marine Corps Band.

Elsewhere around the country, citizens found an infinite variety of ways to celebrate the patriotic day. Before a large crowd at Pearl Harbor, Hawaii National Guard jets flew a "missing man" formation over the watery grave of the USS Arizona, sunk during the Japanese attack on Dec. 7, 1941.

In back yards, parks, at beaches and elsewhere, the only things in the air were Frisbees and the aroma of grilling food.

In Washington, such traditional fetes were aided by the weather, with temperatures reaching 80 degrees, moderate humidity and a 5-mile-per-hour breeze.

Other Memorial Day ceremonies in the area took place at the Civil War Cemetery at St. Elizabeths Hospital in Southeast Washington, and at the Alexandria National Cemetery.

In contrast to the service at Arlington, where almost 200,000 men and women are buried, was a service held by soldiers stationed at the Walter Reed Army Medical Center at the Battleground National Cemetery, the final resting place of 41 Union soldiers who died in the Battle of Fort Stevens in summer of 1864.

But it was the country's most recent war in Vietnam and its veterans that drew Reagan's most evocative words.

"They chose to reject the fashionable skepticism of their time," Reagan said of the Vietnam soldiers. "They seized certainty from the heart of an ambivalent age. They stood for something."

However, most of the corps of veterans who attended the ceremony, had served their country in World War II.

As they huddled in dozens of small groups after Reagan's address, many veterans clearly rejoiced in the camaraderie they learned as soldiers. They sucked in paunches to fit in old uniforms one more year, and swapped good-natured stories of successes and snafus from four decades before.

In between, however, there were melancholy memories of friends lost. "We've got our happy moments," said Mitchell Layman, a VFW member from Broadway, Va., who attended with several members of his post. "It's then that we think of the others. Part of us is gone."