Israel's Merkava tank is a tough piece of hardware. It was specially designed to protect the crew from other main battle tanks. They carefully studied the wrecks of several hundred tanks to find out why they were defeated and incorporated the lessons learned into the Merkava. The design also includes reactive armor to defeat most forms of shaped charged warheads.

The old tactics of blowing up a tank with a Molotov cocktail won't work on a Merkava because of good fire suppression systems. Even suicide bombers wouldn't do much against one. They couldn't penetrate the armor and I doubt if they could do more than blow off a track, if that. To kill a Merkava, you'd need a pretty powerful anti-tank weapon and I guess the Palestineans don't have many of those. I think the Palestineans did manage to destroy one tank a couple weeks ago but the odds are very much against them.