Russia could become a member of NATO. There have been serious discussions to that effect. I can expand this answer if needed by the OP (pls comment below). Currently, Putin's regime appears to want NATO to go back to the 1897
^D^D^D^D 1997 borders, so NATO expanded to accept Russia would be opposed by the Russian regime itself!
The idea of Russia becoming a NATO member has at different times been floated by both Western and Russian leaders, as well as some experts. No serious discussions were ever held.
In 1990, while negotiating German reunification at the end of the Cold War with U.S. Secretary of State James Baker, Soviet president Mikhail Gorbachev said that "You say that NATO is not directed against us, that it is simply a security structure that is adapting to new realities ... therefore, we propose to join NATO." However, Baker dismissed the possibility as a "dream". During a series of interviews with filmmaker Oliver Stone, President Vladimir Putin told him that he floated the possibility of Russia joining NATO to President Bill Clinton when he visited Moscow in 2000.
Anders Fogh Rasmussen, the former Danish Prime Minister who served as NATO Secretary General from 2009 to 2014, said that "Once Russia can show it is upholding democracy and human rights, NATO can seriously consider its membership." According to Rasmussen, in the early days of Putin's presidency around 2000–2001, Putin made many statements that suggested he was favorable to the idea of Russia joining NATO.
Russian leadership made it clear Russia did not plan to join the alliance, preferring to keep cooperation on a lower level. In March 2009, the Russian envoy to NATO, Dmitry Rogozin, while not ruling out NATO membership at some point in the future, stated: "Great powers don't join coalitions, they create coalitions. Russia considers itself a great power."
In early 2010, the suggestion was repeated in an open letter co-written by German defense experts. They posited that Russia was needed in the wake of an emerging multi-polar world in order for NATO to counterbalance emerging Asian powers.
(Wikipedia: Suggestions of Russia joining NATO: https://en.wikipedia.org/wiki/Russia%E2%80%93NATO_relations#Suggestions_of_Russia_joining_NATO )