2005 pontiac montana won't start

Sounds like a bad battery.

Could be fuel pump or fuel relay, sound like you're not getting enough gas.

First thing I would check would be the battery. Open the hood and make sure the battery terminals are tightly connected to the battery (try to turn them on the post by hand). If they are tight and you have a volt-ohm-meter you can check the battery charge yourself. If not you can remove the battery and take it to an autoparts store and ask them to check it for you.

All of these circuits are controlled by the key switch. If the fuses for these circuits are good but have no voltage, I would check the key switch next.

If you have voltage at the fuse and relay, and at the pump, but no fuel pressure, I would say the pump has died or the tank is empty.
Have you checked for voltage at the pump yet ?

Fuel pump won't be the cause. Most likely the relay.

it sounds like the starter motor could be worn out, or could be as simple as the main pos wire is bad or corroded

If the car was running when this happened and now it won't start, I would have to take a look at the starter to see if it got wet and make sure it is not shorted out. Also the wiring from the battery to the starter may be wet and shorting as well as something in the fuse box. IF it is clicking then I suspect you have some power to the starter but not enough to turn it over. If you ran the car for a while after it was wet you could have damaged the altenator and it may not be charging the battery and the battery may be drawn down to where you don't have enough amps to start the car. Try jump starting to see if it is related to the battery if not then start looking for electrical shorts in the wiring to the starter.

Using jumper cables :
1. Connect one red clamp to the positive terminal (+) of running car's battery and the other end red clamp to the positive terminal (+) of the dead car's battery .
2. Connect one black clamp to the negative terminal (-) of running car's battery and the other end black clamp to the negative terminal (-) of the dead car's battery.
Basically... (+) to (+)...and... (-) to (-)
3. Crank up the car needing the jump.
4. Once car is jumped and running...remove clamps in reverse order.

Using battery pack: Connect in the same fashion as above.

did you check you fuses or relay switch?