(CNN) -- The United States takes on Ghana. Ronaldo takes on his left knee. And Iran tackles a giant killer.
Here's what to look forward to during the Monday matches at the World Cup:
Third time is a charm?
U.S. fans had a bad feeling while watching the World Cup draw in December, especially after being picked into a group that included Germany and Portugal.
When it came time to learn the Americans' third opponent, World Cup nemesis Ghana was still on the board. Surely, the soccer gods wouldn't...
Perhaps the third time -- Ghana knocked the United States out of the Cup in 2006 and 2010 -- will be revenge. The two teams meet Monday in a Group G opener
Or maybe it's not payback time.
"There's no revenge factor," U.S. goalie Tim Howard, who was on both previous World Cup teams, said, according to USA Today. "We don't feel that. That's not what's motivating us. We think that they're a good team but we also feel that we are slightly better as well."
Ronaldo feels swell
The body of the world's greatest player is 100% fine.
Well, that's what I've heard.
Wait, we are talking about Cristiano Ronaldo's fitness, are we not?
He told reporters Sunday that when he takes the pitch in Monday's marquee matchup with Germany, the Portugal star said he'll be ready to go even if he's feeling a little knee pain -- and though he's bad at math.
"I'd love to be 110% and but I am 100% and that is enough to help my team," he told reporters Sunday,
Keeping the shirts on their backs
It is traditional for players to swap shirts at the end of a World Cup match.
But Iran's football federation has told its players not to trade.
Not for hygiene reasons, but because they don't want to buy a bunch of new ones.
"We are not giving the players a shirt for every game," Iranian Football Federation President Ali Kafaschian told the semiofficial Fars news agency, according to SBNation. "The players have to be economical with the shirts."
That might be easier to do Monday against Nigeria than Saturday when they play Argentina and Lionel Messi wants to exchange shirts.
Weather or not
Downpours, extreme heat and humidity and even snow. The United States faced all kinds of weather during World Cup qualifying.
Monday, they may get to do it again. When they meet Ghana in Natal, there is a chance of showers.
U.S. coach Jurgen Klinsmann doesn't want to hear questions about the weather.
"If it's raining or if it's snowing or if it's thunder and lightning, or whatever, this is about football being played in any circumstances," Klinsmann told reporters, according to mlssoccer.com.
ESPNfc.com reported 50 homes in the area have been evacuated over flooding concerns brought on by nearly 9 inches of rain this weekend.
Reason to love: Iran
The highest-ranked team in Asia wants to bring the plight of the Asiatic cheetah to the world's attention and has a new jersey with the endangered cat on it. There are only 70 to 110 Asiatic cheetahs left, all of them in Iran, says conservation group Panthera.