Where can I find free games for my mac?

I really really want Metal gear- the most! I also like siphon filter, tetris or the bubble version of it. Those games where you put colors together and the breaks them down. There was this one game on time I kind of liked too, it just had a tiny ball, and you had peddles that bounced it in order to break these bricks, and some times these extra lifes would fall from the bricks, or a "slow the ball down" for speed it up. And it got more difficult each level you went up. I looked at apple's games, but they are only for trials. I want free games to download. Where do I find them at? And where can I find metal gear solid? Thanks in advance!