Four people have been charged and nine others are being interviewed over a "sophisticated" ice syndicate in Melbourne.

A 58-year-old Sydenham man faces a charge of trafficking a large commercial quantity of drugs, while men aged 29, 27 and 52 have each been charged with trafficking a commercial quantity.

They are expected to face Melbourne Magistrates Court for a remand hearing on Wednesday night.

The men are among 13 people aged 26 to 61 who were arrested on Wednesday as more than 100 police raided 12 properties across northwest Melbourne seizing guns, cash and drugs including methamphetamine, commonly known as ice.

Acting Assistant Commissioner Peter Brigham said the group had proved to be a difficult target because "they're familiar with conventional police procedures".

"They are quite sophisticated and versed in investigative techniques and so they're very good at concealing the way they operate," he said.

The organised crime syndicate had been supplying ice to other dealers in Melbourne for a "significant" time, police alleged, with pending charges expected to cover an eight-month period dating back to October.

Drugs including ice, cannabis and cocaine as well as illegal firearms were recovered from properties raided in the suburbs of Sydenham, Taylors Hill, Airport West, Pascoe Vale, Keilor, Caroline Springs, Albanvale and at a factory at Ravenhall.

Neighbours had been "quite uncomfortable" with what they thought had been going on at the properties but did not speak up, police said.

More charges are expected to be confirmed on Thursday.