Metal Gear Solid 4 Walkthrough/Act 1

Act 1: Liquid Sun Walkthrough
When Solid Snake gets off the truck, you must go towards the truck on the left side of the screen, where Snake will crawl under it. Next, Some Gekkos will appear. You do not have to attack; all you have to do is run away from them. You must run to the north. Once you've the area you were supposed to go to, there will be a cutscene.

After the cutscene, some PMCs and a tank will be nearby. You have go to around them to get behind them. The recommended ways are to go along the right side and enter various buildings so as to avoid detection.

Once you reach the point, you will meet Metal Gear Mk. II and will be given the Operator, Solid Eye, and Mk.2.