Sixteen NATO allies have sent a total of about a thousand troops to safeguard the summit, which will take place on Tuesday and Wednesday.
Many are also providing advanced air defence systems the Baltic states lack.
"It would be more than irresponsible to have our sky unprotected as Biden and leaders of 40 countries are arriving," Lithuanian President Gitanas Nauseda said.
The Baltic countries of Lithuania, Estonia and Latvia, once under Moscow's rule but part of both NATO and the European Union since 2004, all spend more than two per cent of their economies on defence, a larger share than most other NATO allies.
But for the region with a total population of about six million people, this is not enough to sustain large militaries or invest in their own fighter jets or advanced air defence.
Germany deployed 12 Patriot missile launchers, used to intercept ballistic and cruise missiles or warplanes.
Spain has brought a NASAMS air defence system, France is sending Caesar self-propelled howitzers, France, Finland and Denmark are basing military jets in Lithuania, and the United Kingdom and France are supplying anti-drone capabilities.
Poland and Germany sent helicopter-enhanced special operations forces.
Others are sending equipment to deal with any potential chemical, biological, radiological and nuclear attacks.
For Nauseda, the allied effort to ensure air safety during the leader's gathering means NATO needs to urgently set up permanent air defences in the Baltic states.
"We think about what happens after the summit ends, and we will work with allies to create a rotating force for a permanent air protection", he told reporters.
At Vilnius airport, eight German-operated Patriot missile launchers were seen standing with their nozzles pointed in the direction of Russia's Kaliningrad.
Two more pointed towards Belarus.
All of the launchers have been operational since Friday morning.
Lithuania has tripled the deployment of border guards at the Belarus and Russian borders for the summer, augmented by officers from Latvia and Poland.
The two countries have also sent police to help patrol Vilnius.
"We are preparing for various provocations", border guard chief Rustamas Liubajevas said.
He said he feared waves of migrants at the border, or border violations, or military vehicles appearing at the border without explanation.
Thousands of Middle Eastern migrants have crossed at the Belarus border in 2021, in an effort Lithuania and the European Union said was orchestrated by Minsk, a charge it denies.
The numbers have since subsided.
"The situation is really very tense, because of aggression of Russia against Ukraine, so the (border protection) was already on a very, very high level (before the summit)," Liubajevas said.
Border checks on Lithuania's European Union borders with Poland and Latvia were reintroduced for the summit.
The mayor of Vilnius has suggested citizens go on holiday outside the city if they want to avoid disruption, as large parts of central Vilnius will be closed off for the summit.
