State Governor Ralph Northam on Sunday declared a state of emergency ahead of the Lobby Day rally, banning firearms from the area around the Capitol building, the BBC reported.
The Federal Aviation Administration has also issued temporary flight restrictions over the city, making it illegal to fly planes or drones.
The rally is an annual event, but several gun-control bills passed in January by the Democrat-led Virginia legislature, in the state where gun rights have historically been permissive, have angered gun owners and activists.
The Virginia Citizens Defence League (VCDL), a gun rights group which organised the rally, said it expected as many as 50,000 people.
Many of the buses laid on from neighbouring states were sold out before the weekend.
Various groups including armed militia, right-wing extremists and local Antifa, or anti-fascist movement, are expected to attend.
Christian Yingling, who led the Pennsylvania Light Foot Militia during the violent clashes in Charlottesville in 2017, told the BBC that he was hoping for a big turnout.
"I'd like to see a lot of people, I really would. I know from chatter online that a lot of militia types are coming in from some distance... Texas, Illinois, elsewhere," he said.
He said he hoped the rally would pass peacefully but feared it would not. "I think there's enormous potential for something to go wrong."
At a rural community hall about 20 miles south of Richmond, dozens of people from different militia groups gathered on Sunday night to talk about tactics for Monday's rally and about the broader threat to gun rights they see in Virginia.
When Greg Trojan, one of the founders of the VCDL, asked how many people had travelled in from outside the state, more than half raised their hands.
Many at the meeting said they hoped for a peaceful day tomorrow, some said they anticipated violence.
( With inputs from IANS )