Following a gloomy 25-stop metro journey from the centre of Paris and a long trek down from the campsite in Parc de Saint-Cloud, it's a relief to hear the familiar, rasping voice of Chance the Rapper claiming to teach English (or just a chant, "uh-uh") to the Rock En Seine crowd. We're on the outskirts of the City of Light, il fait chaud and jazzy, croaking hip hop is the perfect way for our bank holiday weekend to begin.

Chance looks and fulfils the part, wearing a pink flowery hat, his unique IGH ad-lib injecting that much-needed boost of Acid Rap energy. His set peaks with Kanye cover 'All Falls Down', spruced up but pared down, harmonies added on top. The close-knit interplay between him and DJ Oreo is clear. In what nearly ends rather nastily, Oreo leaves the booth during the song, takes a running jump over Chance and lands headfirst on the stage, certainly injuring himself. The former limps off, but the French love it, chanting and jumping despite the saga.

Kendrick Lamar meanwhile, headlining the second stage, is fresh from playing main support to Eminem at the 90,000-capacity Stade de France the previous night. As Lamar puts it, "Sky's the limit" as he plays smash after smash from last year's now-classic . He doesn't look like a star in his modest black hoodie, but he certainly sounds it on 'Bitch Don't Kill My Vibe', whose clattering beat and unremitting verse flow are timeless.

If Belle and Sebastian provide a rare early afternoon slot of ebullient twee, Tame Impala are the ominous counteraction. But a marvellous one at that. Insane levels of wah-wah fill their sound on 'Why Won't You Make Up Your Mind?' and anthem 'Solitude Is Bliss', whose groove, maracas and head swings are the perfect analogy to the weather. They never wax lyrical on any positive notes, but their murkiness is to be admired, especially on a synthed-up version of 'Mind Mischief' and a cover of the Flaming Lips' 'Are You A Hypnotist?'

Our main stage run continues with Franz Ferdinand, who are just as slick as we remember. Returning to the festival they headlined after only one album back in 2005, they still have all the energy of back then, bringing the funk of fourth record Right Thoughts, Right Words, Right Action to a massive, packed out arena. Alex Kapranos' sly, seductive looks are as provocative as ever, posing with his telecaster and commanding the crowd with his frozen gaze and index finger. Classics like 'Do You Want To' and 'Michael' all go down a treat, whilst new song 'Evil Eye', pop short and sweet, is certainly promising.

But no one here comes close to topping !!!, who headline the relatively small Pression stage at midnight. Starting out with only a handclap and a beat, the legendary Sacramento band come on one by one and the disco-punk builds. 'Yadnus' is the fantastic opening freakout jam, hip-thrustingly, shriekingly mad. And from there on in, things get even more exciting. Gestures, expressions and emotions are made, clarified or acted out by totally bonkers lead singer Nic Offer, whilst two awe-inspiring percussionists provide his rhythmic pedestal. 'One Boy One Girl' is the standout in a brilliant, exhilarating set seemingly over in an eyeblink.

Taking a look around on a much colder day two and it soon becomes clear that this is a corporate mega-bash of epic proportions. The main sponsors include RATP, Ile-de-France, France Inter, Grazia, Deezer, SFR, Coca-Cola and Amazon, which is the equivalent of, say, Lovebox being sponsored by National Rail, the City of London, BBC Radio 4, and so on. Ads even play between bands on the screens. No worries though, because we're having a great time regardless.

For instance, there is a bibliothèque. Yes, a library. There are many shelves, with comic book, rock'n'roll and fiction sections. There are beanbags and library assistants. Later today, there is apparently a 'history of rock' dicté, a dictation, something poor little French kids have to go through at school on a daily basis. But grown-ups at a festival? One word: surreal.

Saturday's line-up is rather empty of great musical substance early on, but La Femme's superb mid-afternoon set provides more than enough belters to make up for the initial lull. The francophone act from Biarritz are the hottest thing in France at the moment and, quelle surprise, the crowd is massive. They are certainly stylish, all army coats, 50s secretary wear, vests and blonde bleach.

Sound wise, brilliantly chaotic synth lines follow on-going drum rolls whilst eerie boy-girl harmonies float above, matching grumbling with delicacy in that classic Gainsbourg-Birkin vein. All their songs are long, upbeat and charging, and they have every single witness on side. There's a good lot of jigging along, handclaps everywhere and the band's kooky dancemoves play as much a part of the show as their music. The syllable-timed French tongue lends itself perfectly to their jerky but systematic beats.

Experimentation is the word. Everything feels like a jam. Ghostly synths, clunky beats and singer Clara Luciani's sky-high voice give their overall sound a general sense of whimsy and loveable backwardness. This silliness is amplified by their interaction with the crowd, most notably when the guitarist, wearing a Hawaiian shirt, swaps his axe for a surfboard. Undeterred by the scale of the task, he allocates crowdsurfing its most literal interpretation and - literally - surfs the crowd. This is a band obviously having rather a lot of fun, and songs like 'Antitaxi' prove the enjoyment is vibrant, productive, and profitable.

We've been spotting Nine Inch Nails tee shirts all day and have deduced that roughly 60% of the crowd here today are for Trent Reznor and Trent Reznor alone (it's his band's only gig in France this year). As for their set, their insane, excessive light wins it. Reznor is as focused and emotional as ever. And although their music is, as usual, a little bit headachy and overzealous for our tastes, their big phat bass-lines and ear-splitting riffing (I'm not a metal journalist) are certainly a little bit cool.

And who better to follow them than Phoenix? Unsurprisingly, there is a dramatic crowd shift as the middle-aged noirish depart and a happier, younger, less angry faction rush and ready themselves to mosh along to arguably the second biggest French band in the world right now.

A delight from start to finish, they bring along the same stage show they used to headline Coachella (minus R Kelly) and the result is pomp and pyrotechnics mixed with Parisian-ness and professionalism. Whether it's entering the stage via buggy, firing thousands of custom-made money notes reading 'ZERO POUNDS' into the air, or the moment frontman Thomas Mars enters the audience, reaches the back and crowdsurfs over the whole lot, all the way back to the stage, this nothing short of a headline spectacle and one of the greatest shows we've ever seen.

Oozing confidence and coolitude throughout, they rattle through a set of hit after hit. A brutal moshpit forms and never decomposes. 'Lasso' and 'Lizstomania' from their breakthrough album Wolfgang Amadeus Phoenix are still absolute bangers, whilst early single 'If I Ever Feel Better' is similarly triumphant. Songs from the new album also sit perfectly and everyone wants MORE OF IT ALL. A rare occasion.

By the time we head out of the tent and make our way down to the arena on Sunday, it's been raining for fifteen hours straight. No respite, just patter-patter-patter. Fortunately for us, the stony ground leaves the site relatively mud free.

The first band we manage to see are Minneapolis act Poliça, who seem a little demoralised by the wet. They're here to promote their second record, the darker-sounding Shumalith, due this October. Filled with live drums, violent rhythms and prominent poppy synths, all electronic beats removed, the new songs possess a compelling force on stage.

The two drummers, in their own little worlds, are on heady, deafening form. Singer Channy still moves around the stage scowling and dancing ethereally, controlling vocoders and auto-tune live. The bass rattles the speakers. Each band member is so utterly consumed by what they're doing. 'Say My Name' and the Justin Vernon-featuring 'Tiff' work brilliantly live, and so do new improvised verses on 'Dark Star' and 'Lay Your Cards Out'.

Next up, on the same Pression stage, NY duo MS MR play out a set of sugar-sweet pop anthems. A cover of LCD Soundsystem's 'Dance Yrself Clean' and vamped-up rendition of hype machine legend 'Hurricane' are the pick of the bunch, but most striking is the simple ebullience on show. Max and Lizzy are two of the most cheerful looking people we've seen all weekend, smiling throughout, dancing non-stop and unashamedly. Also, Lizzy's hair is now green and orange: boldness certainly to be admired.

But we can ditch the happiness. Gritty, loud and sarcastic, Parquet Courts are easily the band of the day. Resembling a group of scruffy sixth-formers or an unassuming gang of punk rockers, they veer from plodding, chugging slacker rock to frenetic, rousing hardcore, never letting their beautiful discordance stray.

In essence, their squalling, garage freakouts are a wonder to behold. Take 'Stoned and Starving', a sweat-shaking, feedback-drenched hymn to the not-so-high life. It's utterly brilliant and showcases a youthful vigour and humour. Picking at the French in a snarling, comic way, their guitarist lets us know he still hasn't found that "mayyynage ayyy trois" yet and the crowd applauds unwittingly. Basically, the band totally don't give a shit and that's why we love them.

Diplo's Major Lazer are left with the honours of closing the festival and they bring along a pantomime. The band are A-list stars in France, much more so than in Britain, and you can tell this by the crowd-size. The next hour involves, amongst other popular quirks: foam-shooting, goodie bags, twerking, clichéd shoutouts to weed-smokers, harlem shaking, getting low, butt-shaking, UFO-sighting and lots and lots of drops. It's all very hard to take seriously, but they certainly know how to create a party. Notably, they bring on French star Stromae, who recently reached number 1 in 17 countries and is currently on the front cover of GQ France, and the teen-dominated audience goes wild. His hit 'Papaoutai' is slightly strange but enjoyable and comforting, a bit like this festival as a whole. To next year.