As an example game of the Modern defense with 4...Bg4 I just have to use the game between Boris Spassky and Robert James Fischer played during the world championship of 1972 in Reykjavik.
1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.Nf3 Bg4 {This is the main line of the Modern Defense
