First Night: Lady Gaga, 02 Arena, London

Shocked and thrilled by Gaga's theatre of excess

"the monster's Ball will set you free, London! Tonight we're gonna be super freaks!" And so begins an evening in the company of the world's biggest pop star.

Time magazine may have just voted Facebook founder Mark Zuckerberg as their "Person of the Year", but for millions, it was a 24-year-old New Yorker with a steak on her head. It would be an arduous task to list all the accolades bestowed on Gaga these past 12 months, but her triumphs were impossible to escape from: a world record broken here, another award won there.

Everyone seemed to have an opinion and Gaga came under the sort of scrutiny that is usually reserved for those governing countries or running corporations. For every person who has fallen for her, another has come at her with knives, as minute details of her narrative were picked apart and contested. Was she a phoney? An identify thief? A man?

When so many people dedicate themselves to something so profoundly, as do her legions of fans, or "little monsters", there will be critics keen to bring down their hero. With all the arguing about commercialism and feminism, it became easy to forget that Gaga is just a pop star: she sings songs for the entertainment of others.

And here she is doing what she does best: performing. And, boy, has she been busy with it. Away from the headlines, the outré costumes and the controversial soundbites, Gaga has been working like an ox. Her Monster's Ball tour begun in November 2009. So far she has completed a staggering 156 shows, taking her to four continents. And when it wraps in May next year, the tour will have made an estimated $200m (£130m).

Not that the slightest sense of ennui pervades the show, which is as energetic and fresh as it is theatrical.

The evening – imagine a Tim Burton-directed musical with the cast of RuPaul's Drag Race – is everything a great show should be: shocking, funny, even moving. The extravagant sets and camp routines that accompany those oh-so familiar pop songs are all present and correct. And at the centre of it all is the Lady herself. Swearing, titillating us with lurid tales, beheading a Santa, casually throwing out one-liners, getting covered in blood: she does it all.

It's not without its lulls. At two hours long, the show is made up with its fair share of filler. No matter how much Gaga has influenced, even dictated, the cultural landscape over the past two years, it should be remembered that she has released just one album (two if you insist on including her extended re-release, The Fame Monster). Her back catalogue doesn't stretch to that of the seasoned performers who usually fill these arenas. While no one would suggest artists need to wait for their bus pass before taking on venues of this size (the demand is there, after all), it does mean that acts end up killing time with lesser-known songs and dubious guitar solos. And while the outfits are great, they were all disappointingly familiar. Part of the reason to come to a Gaga concert is to see what she will deign to put on (or not put on, as is often the case.)

She manages to combat the impersonal nature of the arena show with stories and jokes directed at different groups in the audience. She even tells us reviewers to dance and go get a drink (OK, Gaga!).

It's hard not to be touched by the sincere way she talks to her fans. And when you find yourself becoming cynical and suspicious at the incongruous nature of someone who has nominated themselves as a mouthpiece for every freak and outsider, in front of an audience of 23,000 people, you shake it off. Because an evening in Gaga's theatre of excess is such good fun. And, really, isn't that the point?