How can I beat the Battle Tycoon in Pokemon HeartGold!?

I can't beat him in first battle! I've used the right pokemon with great states but I still can't beat him! My gallade has got some critical hit moves and different type moves. So does my Scisor and Arcanine! I'm getting a Metagross and a Electrivire And see how it works out. So I need some help how to beat Palmer in HG.