Go to Pewter City and talk to an old man. The old man will give you a Silver Wing. With the Silver Wing, go to Route 41 and enter Whirl Islands. As you explore Whirl Islands, go down a large waterfall and enter a deep chamber where Lugia awaits. Save your game before you interact. Lugia is on Level 60. It will combo by using Rain Dance then Hydro Pump. If it runs low on HP, it will use Recover. Use Ultra Balls and moves that induce sleep, like Hypnosis.
MAG.MOE - The MAG, The MOE.