Ighalo completed a six-month loan deal from Shanghai Shenhua on Friday, three years after he left Watford.
The 30-year-old is expected to boost their attacking options with Marcus Rashford ruled out for a couple of weeks with a back injury.
Commenting on the loan deal, Stam, a former Dutch international expressed optimism that Ighalo will score goals.
‘He’s got nothing to lose because nobody thought he would be a United player,” Stam told SkySports.
“United have the confidence in him. We’re all a bit surprised, but he can just go in there and do his thing. We all want to see United get back up there.
“Like all former players and United supporters, we wish him well. He’s joining a big family. Everybody within the club hopes that every player will do well and is going to perform.
“I’m sure he’ll feel welcome and hopefully he’s going to produce.”
Stam added: “He’s now playing with better players than he was at Watford, so he will get more opportunities to score than at Watford.
“I’m sure he’s got the ability. He wasn’t their first choice, but you assume people have seen him and trust what he can bring.”
Meanwhile, United’s other signing Bruno Fernandez made his debut in Saturday’s 0-0 draw against Wolverhampton Wanderers at Old Trafford.