Siege tanks are obviously a very powerful ground unit of the terran. Even if you get just 2 siege tanks it is important to get their upgrade, siege mode. It is so important when getting tanks I am surprised they sis not make it a natural ability. But I guess if you did not have to research siege mode at the tech lab then Terran really would be OP. Siege Tanks are very good against such units as... protoss stalkers and sentries terran marines, marauders, hellions, and ghosts zerg hydralisks and roaches But they suck against units such as immortals, zealots, zerglings, and any air unit that can attack ground units like banshees, mutalisks, and void rays. They are ideal to get for when you decide to play defensive whether you are facing a rushing protoss player or decide to expand early. It is best to have them placed behind a wall for defense and behind units when on the battlefield. Mixing them with marines, marauders, and even thors is a powerful combination when up against a heavy ground army. Not a lot of terran players realize this but massing siege tanks in late game is usually what you want to do especially when facing protoss units as their units are powerful and having just marines and marauders up against an army of gateway units and colossi is not going to cut it. Siege tanks require good micro. Tou need to protect them while also spreading them out before getting into siege mode. You do not want to bunch them together and siege unless it is at the last minute and your opponent is rushing with their units. Have one a distance from the other especially when facing an army of melee units like zerglings or zealots so one can protect the other. Already having them in siege mode before you face your opponents army is obviously what you want to do since it takes about 4 seconds for them to get into siege mode. They have such long range they can attack beyond their vision. That is why having air units like vikings with them is a powerful move especially if you are attacking them on the low ground to give them vision. Against terran siege tanks are usually great to have against marines, marauders, or even thors. If your terran opponent walls off then you can easily take them out with an air unit even if they have tanks defending from behind their wall. Always be sure that owhen you move out with your army you have your marines and marauders a good distance in front to protect the tanks and even make your opponent retreat with their units. Some sneaky moves to watch out for when in game is roaches with tunneling claws since they can ambush the tanks in siege mode so they are too close to attack. Be sure to have detectors in this scenario. Also blink stalkers can quickly surround them if you are not careful. Terran players will try to keep vision on your tanks with marines and marauders nearby so that right when they see your tanks get out of siege mode they will stim pack right in to try and take them out and then pull back. Of course you should have anti air with them if you are up against mutas, banshees, void rays, and even phoenix since they can use their gravity beam. Feel free to add something to this like build orders.
another thing that should be added (especially cause raynors a terran player) is the weapons upgrade for tanks is extremely powerful against zerg. Baneling busts in particular. With 1 weapon upgrade into tanks, they will one shot banelings, even if the banelings have 3 into armor. Great little tip to know!
Banelings have 30 life and 0 armour, even maxxed out they only take 33 damage to kill, tanks do 35 damage by default i think u missed a few stats brahski