He still needs time to settle in, says boss...
The Ghana international made a deadline day switch from Rennes after a fee in excess of £13 million had been agreed with the French club.
Bruce tried to sign the striker during his Birmingham City days, while eyeing the player once again last season - prior to signing Darren Bent - before finally being third time lucky.
"I went to see him play for Ghana against Senegal at Millwall something like three and a half years ago when he was at Udinese, and he caught my eye that night," Bruce told reporters.
"I tried to do something the following summer and couldn't, and then he went to Rennes and I tried 12 months ago before Darren Bent came here.
"We had a little sniff, but when Darren became available, I opted for Darren because he had already played in the Premier League.
"But we had chased him and monitored him a long, long time."
Having signed on deadline day, Gyan had to immediately leave to represent his country in the qualifiers for the Africa Cup of Nations.
But following the international games, the hitman returned to Wearside to join his new team-mates on Thursday.
"Like anybody, he needs time to settle in," Bruce said. "He is a larger than life sort of character, he is one of these who loves life and plays that way too.
"When you see him, he has got this energy about him and he has got this way how he lives his life too, which is going to be colourful, if I put it that way.
"But that is what we have bought. He enjoys playing, he enjoys life and I am hoping he can have a really good time here."
There had been suggestions that the 24-year-old could be handed a debut when the Black Cats travel to play Wigan Athletic on Saturday.
Bruce added: "Will [he] get a game? That's one way of putting it. Well, he is in contention. I have paid a hell of a lot of money for him, so I would expect him to play some part in the game."