Some 45,000 Foregophiles turned out at Belmont Park today to see the three-time Horse of the Year begin his bid for another national championship.

They came to hail Caesar and Forego ego, the sport's reigning emperor, responded with a brilliant rally from far off the pace to win the $114,400 Metropolitan Mile by two lenghts as the 1-to-2 favorite.

It is a treat to see the way New York racing fans respond to the champion. They applaud when he appears in the paddock. They cheer him as he moves onto the race track. The cheers build to a crescendo as the big hourse makes his patented stretch charge - and an ovation waits when he is guided into the winner's circle by Bill Shoemaker.

Even the losing bettors appear to join the spirit of the occasion, once the race is over. Here in the heart of the hard-bitten Big Apple, that's something.

Forego carried 133 pounds today in beginning his fourth try for the Handicap Triple Crown. The weight was his major obstacle, and he overcame it smartly with a punishing run six horses wide that carried him from eighth place at the quarter pole to the lead a few strides after the eighth marker.

"That's the only thing that worried me, a little. The fact that the . . . got to the lead quicker than I wanted," Shoemaker declared. "He sometimes will relax a little on you, after that. Today he didn't. He kept it going to the finish."

Co Host finished second, two lengths ahead of Full Out, with It's Freezing fourth. Soy Numero Uno, the 3-to-1 second choice, wound up eighth in the field of 12. Forego's time was 1:34 4/5.

A half-mile from the finish Forego again appeared to have little chance. He was 10th, approximately 15 lengths behind the front-running Barrera. His backers had to be worried. Shoemaker wasn't.

"I couldn't feel him getting in gear," The Shoe said. "He had that momentum. Soy Numero Uno was the horse we were following. He was the one to beat, we though. When I saw tht horse wasn't responding for (Ray) Broussard, we took off past him. I didn't have to do anything more than show Forego the whip, about the eighth pole.

"This horse is an old pro," Shoemaker added. "He's 7 now. You don't have to urge him into what to do. He knows what's expected. He's the best I've ever been on."

Shoemaker is undefeated on through four races. They teamed up last fall.

Forego's next objectives will be the Suburban and Brooklyn as he attempts to become the fourth thoroughbred to sweep New York's three major handicaps in one season. Kelso, Tom Fool and Whisk Broom are the only horses to have done so. Forego missed by a nose last season, in the Suburban. He is now 6-for-10 in the three events over four years, always under high weight.

Today's triumph, worth $68,640, increased Forego's earning to $1,738,857. That moves him within a neck of Round Table ($1,749,869) and only a couple of lengths away from the world recordholder, Kelso, at $1,977,896.

Forego now has won 31 of 50 starts, including 22 stakes. The Met marked his second race of 1977. Only age, and perhaps Seattle Slew, appear able to keep him from another Eclipse Award.

"He's like me; he's getting a little age on him," trainer Frank Whiteley quipped on the way back to Forego's born. "He has his little aches an pains. You're never sure just how much longer he can keep going. But we're hopeful. He had a good winter in Camden (S.C.), expet for the cold weather."

Seattle Slew, the undefeated 3-year-old colt, is not likely to challenge Forgeo until the fall in the weight-for-age classics.

Until then, Forego's biggest probblem will be in watching his waistline - the amount of lead pads placed in his saddle bags. The 133-pound impost didn't stop him in the Met. Yet the assignemnts for the Suburban and Brooklyn in July will be heavier, even though the distances stretch out to a mile and a half.

There is always the possibility a longshot, carrying light weight, can trip up Forego along the way, as has happened in this series in 1974, 1975 and 1976. Co Host carried 111 pounds today. Full Out had 115. Only Soy Numero Uno, under 127 pounds was in Forego's weight league and he failed badly.