amp question

i'm new to leds and still trying to learn and have a question about amp draw. on a car/truck there are many lights and other things that the battery has more amps then the components need, and they only draw what they need. i have looked and i can not find the answer and may be wording it wrong. if a led chip is rated at 12 vdc at .2 amps, and hooked to a battery that is 12 vdc but 500 amps. would it only draw what it needs or would it burn out? please don't bash me as i can wire a car/truck top to bottom, front to rear, but the leds are new to me. thank you.

There is a difference between Ah and A.
Ah is the capacity of the battery (the current that is delivered when the battery is emptied in one hour) A is the current.

You will also note that LEDs are very voltage sensitive, and would rather be current-regulated. i.e. if you control the current, you control the light output. You can do so with voltage too, but you have to know the EXACT Vf specifications of the LED, including current draw relative to Vf.

Your best bet would be to find a 200mA constant current regulator that is capable of using an input of 12V. It will only allow 200mA of current through, at whatever voltage the LED requires. The "leftover" voltage is burned as heat in the regulator.

You can also use a LED wizard to calculate what resistor you would need, but keep in mind that most resistors are only capable of dissipating ~1/4W, and if your input voltage changes, so will the output, so might not be the best solution for a device whose input voltage is not always 12V.
http://led.linear1.org/led.wiz

Also, a friendly reminder, please avoid modifying your exterior lights, as these are not fashion statements, but rather, safety devices. Much time, effort, research has been put into defining the characteristics that make up a legal external lighting system to ensure that all parts are safe, and do not interfere with other parts of the system. Kind of like when you see a Civic with a PnP kit, and you can't even tell that they have their turn signals on because their headlights wash out everything else. I figure you were using your car/truck wiring experience as an indication that you have worked with electricity to some extent, not that this device you are building is meant to go on a car, but just wanted to be clear.

Incandescent lights are resistive by nature, which in turn means they have a self-imposed current limiter. LEDs aren't resistive, so unless you put in something else to limit how much current they can draw they'll just pass through as much current as is available, unless/until they go . The rated current is how much they are recommended to go up to, but there's nothing inbuilt that stops them passing through more; hence why a 3Amp rated Cree XM-L can be pushed to 6Amps or more if you are really careful with how it is heatsinked.

PS. I honestly still don't have much clue about the indepth electrical functioning of LEDs, so the above may have flaws and isn't definitive, more an "in a nutshell" statement

thank you folks for the answer. that is what i was thinking but i couldn't find the answer anywhere. i used the 12 vdc as a example. i also tried to tell yall thank you the other day, but i guess i didn't post it right.