Lukaku arrived at Old Trafford from Everton for £75m last week.
And Kompany, who plays alongside the 24-year old with Belgium, believes Lukaku's ability to score goals could be the missing link for United to win their first title in four years.
He said: "Romelu has got one incredible ability. It is his desire to score goals.
"A lot of people have commented on Romelu over the years and he has taken a lot of criticism.
"But his biggest strength is his belief in himself and the ability to always score goals and have that drive constantly.
"I think that is what Manchester United bought and that is what they are going to get from him.
"Therefore they have added a good player to the squad and it is going to increase the competition in the Premier League for the title.