There's a pivotal scene in Godzilla where the titular monster emerges from shrouds of mist and dust towards the audience. He reaches his head forward, opens his gigantic mouth and his iconic roar bursts forth like a shock wave, the Chinese lamps strung across the street in front of him buffeted in the wind from his mighty breath.

Just when you think Godzilla's going to stop, director Gareth Edwards steps it up a notch. Godzilla's head fills the frame a bit more, his mouth opens a bit wider, the roar gets louder and angrier and the lines holding the Chinese lamps snap under the onslaught.

That's the Transformers franchise in a nutshell, and Transformers: Age of Extinction in particular. Michael Bay – with phenomenal amounts of clearance, access and money behind him – has never shied away from the thought that 'no, this is just too big, loud and destructive'.

Where there's somewhere bigger and louder to go, he goes there. And when you think he's reached a climax, he goes a bit louder and bigger just like Godzilla's roar – and that goes for his career, the plot of Transformers: Age of Extinction and the sensibility behind his action scenes.

From the trailer, you'd have thought Cade Yaeger (Mark Wahlberg) – might as well have call him 'America Q StarsandStripes' – is a junk or scrap metal dealer. But he's a roboticist and inventor, albeit the most muscular and rednecked you've ever see... who happens to own a farm. He also has a suspiciously hot teenage daughter who dresses like a country girl apart from the towering heels, but at least Bay had the good grace to make Tessa (Nicola Peltz) his daughter rather than his love interest.

It's ten years after the destruction in Chicago at the end of Transformers: Dark of the Moon and the world is over the transformers' presence, the powers that be hunting them down in order to get rid of them. But among the scrap Cade picks up to strip down and resell, he finds the broken down semi-trailer form of Optimus Prime.

All Optimus needs is a quick recharge and the fight's on again, with a nasty Decepticon on his way from outer space to find something and do something for some reason (explosions) to do with (destruction) some talisman (carnage) etc etc....

So little of the plot by Ehren Kruger makes sense you give up trying to follow it. It's got something to do with a technology firm led by Stanley Tucci who's researching the metal the transformers are made of and hopes to make it the material of tomorrow. What he doesn't know is that the new breed of transforming metal he's developing has somehow come from Megatron, whose computerised DNA still resides in it somehow and is going to take over the world when the new miracle stuff finds its way into every appliance, tool and machine.

Like every other instalment, Extinction teaches us not to be either upset or glad when a transformer dies – they'll be brought back for every sequel by some mechanical/computerised means. But it gives the same old battle between the Autobots and Decepticons the means to emerge again. The CIA is also involved, with a fearsome deputy director (Grammer) in the pocket of the industrialist, and the other transformers bad guy who flies his giant spaceship to Earth and hovers over Hong Kong sucking up boats and cars like you've seen in the trailer.

It makes as little sense as anything else in the movie – it's just the way an alien searches through a city for something in a Michael Bay movie. Another example is the giant transformer dinosaur/dragon things Optimus and the good guys awaken to ride into the battle. Why some transformers are 'human' like Optimus and others are 'animals' is never explained, and nobody really questions the wisdom of letting these enormous metal creatures loose again into the forests surrounding the city after they ride them into town like knights on steeds.

Like everything else in the Transformers universe, they're just an excuse to crash through a populated area and cause as much explosive destruction as possible. The CGI and effects throughout are incredibly well done as they have been in every other Transformers movie, but as soon as you glance away from the flashy colours and movement and wonder how the story actually works the whole thing falls down.

Once again it's a strange blend of realism and childish silliness. Military hardware rolls along city streets below to the realistic-sounding dialogue of warfare deployment while up in the alien robot spaceship they all talk like Penelope Pitstop characters. They even have slobbering transformer guard dogs that make no logical sense in the real world the whole thing is supposed to be taking place in.

Transformers: Age of Extinction depicts the citizens of Earth as curiously inured to the existence of metal alien beings who assume the forms of the vehicles and machinery we've invented. I can see how those out in the real world off the screen might be feeling a bit the same.

And to more of a degree than any big budget movie of the last 20 years, it's more of a challenge spotting a frame that doesn't contain product placement than trying to check it off when you see it. It's a particularly giant jelly-wrestling pit for automotive brands – even the Internet Movie Database Trivia entry for the movie mentions a Transformers Manager of Global Brand Development.