Inter is three points adrift of city rival AC Milan at the top of Serie A ahead of a key week that sees it face Fiorentina in the Coppa Italia and champion Juventus in the league.
Lukaku has made an impressive impact at San Siro since joining from Manchester United in 2019.
He scored 34 times in all competitions last season and has already racked up 16 goals in 2020-2021.
The Belgium international's 12 league strikes this season are second only to another former United star, Juventus forward Cristiano Ronaldo (15).
Barella has relished the chance to play alongside Lukaku with Inter.
"He has physical power like Shaquille O'Neal: they make power their greatest strength," Barella said. "Nobody can move him - even in training, three players are needed to stop him. But he is also so much more [than power].
"Romi is a great leader: he manages to have a good word for everyone, he has a good relationship with everyone and then on the pitch he is decisive like no other.
"He arrived and it was incredible: he already spoke Italian! But for him it must be easy, he knows all the languages of the world!
"He is a force of nature."
Inter improved to second place in Antonio Conte's debut season last year, though it is still waiting for its first trophy since 2011 after agonisingly losing the Europa League final to Sevilla.
"Losing the Europa League final was the biggest disappointment of my football career," said Barella, who praised the coaching of Conte.
"We deserved it, deserved to win that cup.
"At home I am very ordered and now I'm becoming a little bit like that on the pitch too, all thanks to Antonio Conte.
"Before I was more free-spirited, now the coach has given me many ideas, he taught me to choose the moments. I study a lot on the pitch.
"Playing with great champions I try to steal something from each of them, I observe them and I try to make the best parts of their game mine."