History tells us that if you think the Los Angeles Rams win Super Bowl LVI, don't worry about the 4.5-point spread at BetMGM.

It also tells us that if you like the Cincinnati Bengals to cover, you better expect them to win straight up.

For as much time as we talk about the Super Bowl point spread, it has rarely mattered in the betting outcome. Meaning, it's very rare for an underdog to cover and not win the game outright.

In the first 55 Super Bowls, only six times as a favorite won and not covered the spread. It hasn't happened in 13 years. And every time the underdog has covered and not won the game straight up, it has been a larger spread than the 4.5 points we're seeing for this year's Super Bowl.

Here's a quick rundown of the six instances of the spread mattering, with the historical lines from Vegas Insider:

Super Bowl X: Steelers 21, Cowboys 17

The Cowboys were 7-point underdogs. A touchdown pass from Roger Staubach to Percy Howard in the final two minutes gave Dallas the backdoor cover (that ended up being Howard's only NFL catch). The Cowboys had a shot to win at the end but Staubach was picked off.

Super Bowl XXIII: 49ers 20, Bengals 16

Bengals spread bettors might like this omen. Cincinnati was a 7-point underdog in this game. Their cover was rarely in doubt. But the straight-up outcome changed in the final minute on Joe Montana's touchdown pass to John Taylor. Still, through the first 22 Super Bowls before this one, the spread only mattered once.

Super Bowl XXX: Cowboys 27, Steelers 17

Another Cowboys-Steelers game. The powerhouse Cowboys were 13.5-point favorites. Dallas did lead by 13 on two separate occasions but the Steelers hung tough and had a chance to win before a late Neil O'Donnell interception to Larry Brown set up Dallas' game-clinching touchdown.

Super Bowl XXXVIII: Patriots 32, Panthers 29

The Patriots were 7-point favorites. The Patriots took a 29-22 lead in the final three minutes, setting up a possible push, but the Panthers answered to tie it and then a kickoff out of bounds set up a game-winning Patriots field goal. That meant the Patriots won but the Panthers covered.

Super Bowl XXXIX: Patriots 24, Eagles 21

For a second straight year the Patriots won but let down bettors who took them as a 7-point favorite. The Patriots led by 10 in the fourth quarter but a touchdown by the Eagles with 1:48 to go got Philly the backdoor cover.

Super Bowl XLIII: Steelers 27, Cardinals 23

The Steelers make the list again. They were 7-point favorites and led by as many as 13, but needed to pull off the straight-up win in the final minute on Santonio Holmes' fantastic touchdown catch in the end zone.

The common thread for those six games is the spread was at least seven points in every one (exactly seven in five of the games, 13.5 in the other). That means if the Bengals are to cover the spread but not win the game, they'd be the first underdog of less than a touchdown to ever pull that off in a Super Bowl.

That doesn't mean the Bengals can't win. There have been 18 underdogs to win straight up in Super Bowl history. It just means that, in terms of Super Bowl history, if you like the Bengals it might be best to take them on the moneyline at +165 instead of grabbing the 4.5 points.

Unless you think some Super Bowl betting history will be made on Sunday.