Pundits expected a struggling start to the season for the North London club after they lost top scorer Robin van Persie to Manchester United but Arsenal have hit really their stride in the last couple of weeks.
After a couple of disappointing goalless draws to open their campaign, Arsenal beat Liverpool 2-0 at Anfield, thrashed Southampton 6-1 at home and on Tuesday enjoyed a perfect start to their 15th consecutive Champions League campaign.
"We have had a decent start to the season and we have kept the run going, and that is important all round, for the whole season," assistant coach Steve Bould told reporters in Montpellier.
"We have got great team spirit and I think that was evident tonight. Everybody is digging in and things are looking OK."
Arsenal displayed their familiar attacking flair in the first half at Montpellier, then focused successfully on their defensive efforts when the Ligue 1 champions, roared on by a passionate crowd, mounted a fightback.
The Gunners, who have conceded just two goals in five games so far this season, managed to preserve their lead with authority, leaving Montpellier with only a couple of chances to equalise.
Midfielder Abou Diaby said the manner of their victory after going a goal down to an early penalty was a boost ahead of Sunday's trip to Manchester.
"It is important to start the Champions League with a victory but it is also for everything that comes next," he told reporters. "It gives us more confidence."
City should, however, be a harder trip for Arsenal, who failed to really get going in the Premier League title race last year and ended up 19 points behind the two Manchester clubs in third place.
"Of course Sunday is a tough test," Bould said. "We go in there with a bit of confidence, with everybody believing things are going okay. But it is a proper test and that is what we want to do.
"Hopefully we can come through the other side and say we have done okay again on Sunday. Everybody is fine, touch wood.
"Things are looking quite bright."
