A former Metro Trains employee and CFA volunteer has pleaded guilty to numerous arson and sabotage offences, including derailing a train in Melbourne's north-east, igniting grassfires and setting a fire station alight.

Nicholas Archer, 28, admitted to damaging signalling equipment at several train stations in Melbourne's west last year, including Tottenham, Sunshine and Newport, in an effort to cause major disruptions for passengers.

Archer twice targeted the Newport Steam Rail Club in Melbourne's west. ( ABC News )

The Waterford Park man's offending culminated in him derailing a train at Hurstbridge last November, which caused significant track damage and delays for commuters.

At the time, Metro said it had caused millions of dollars of damage.

Archer also admitted to setting the CFA station at Clonbinane on fire last June, where he volunteered.

In December, January and February he also lit numerous grassfires in the area.

Archer also set fire to four 100-year-old rail carriages and two heritage-listed warehouses at the Newport Steam Rail Club in March last year.

He targeted the club again in August, damaging a warehouse and train carriage.

Archer damaged the Newport Heritage Museum, owned by the Newport Steam Rail Club, in November 2009.

He will return to court in October for a pre-sentencing hearing.