Hamilton, running medium tyres, was 0.452 seconds ahead of Verstappen on the soft compound.
Valtteri Bottas was third, 0.525s down on teammate Hamilton.
The usual second practice will be replaced by an hour-long qualifying session to decide the grid for today’s ‘sprint race’ qualifying. It is the second race this season in which an F1 weekend’s format has been tweaked, after July’s British Grand Prix.
Aston Martin’s Lance Stroll was a surprise fourth fastest, with teammate Sebastian Vettel sixth.
Both Aston Martin and Alpha Tauri are midfield teams who appear to have good pace at the low-downforce Monza Circuit. (BBC)