There have been moves in both Finland and Sweden to join NATO, and I suspect todays actions by Russia make this much more likely.
Both used to be staunchly neutral, with Finland operating MiG aircraft until the mid 1990s. However, in recent years both have participated in bilateral exercises with NATO member countries, including allowing overflights of US reconnaissance and bomber aircraft. Neither country now operate any Russian/Soviet hardware AFAIK, and are participating with western/NATO countries more and more.
But even if you are a member of NATO, you are going to have to fend off the opening attacks on your own, using your own armed forces under your own sovereign control. Invoking Article 5 is going to take days to have any real effect regardless of who you are. Sad as it is, Ukraine aren't in NATO, and can't depend on the external assistance NATO cover would provide.
However, any incursions into Poland, the Baltics, Romania or Bulgaria which are NATO countries will provoke direct military action. We've just got to hope Putin understands that.