Shocking video has emerged of a man pummelling another car's window with an object during an angry outburst on a Melbourne road.

The footage shows an armed man emerging from a white ute approaching a car stopped at the traffic lights in St Albans on Thursday afternoon.

He then forcefully hits the window using what appears to be a tow bar, causing glass to shatter.

The victim captured the ute driver's outburst on camera. (Supplied)

9NEWS has been told the victim, 21, was travelling in the area in his car when he noticed the ute driving erratically and cutting him off.

The car driver claims he signalled to the ute driver that he was acting dangerously, prompting the violent outburst.

Another man in the ute spat at the 21-year-old's car off-camera.