User Recommendations for Code Geass: Lelouch of the Rebellion

Both aboput war and suffering, but Full Metal Panic has a funny side to it as well. Although the stories are different, they are both about the war against different countries and using robots to fight.

FMP is much lighter, with a greater amount of comedy, but both are excellent series that have highly-intelligent characters, war, romance, mecca and a good story

Two of my absolute favorite mech anime. Both feature semi-realistic giant robots. In both, a soldier (/ rebel leader) attends a high school while hiding his identity. The conflicts involve mind games, strategy, close combat and/or politics. Code Geass has more twists and turns and is more packed with content in general, while FMP is more focused. Both have great comedy.

They share the same basic concept of war and strategy. And also the use of robot machines that beat the crap out of stuff.

If you liked FMP, you'll likely enjoy Code Geass because they both have a lot of mech fighting, are centered, at least most of the series, around high school, and have some mysterious powers endowed within the main characters.