user47552: I am trying to make a cooler using Peltier Modules, the Peltier Modules and the fans switch on when the Temperature sensor attached to the circuit reads above a certain threshold. But I know that Arduino can only handle a couple of MilliAmps as its functionality, in such a case, how can I control my 480W circuitry (12V/40A) using Arduino? 
I'm very new to all this and will appreciate a detailed answer.
EDIT: To the best of my knowledge, this is not a duplicate of another question as the other question says I'm currently working on several projects that each require controlling devices ranging from 800mA to 2A from an Arduino Uno., whereas my application requires much larger current than that.

user10394: You are correct the Arduino can only handle a few mA at 5V.  In order to do what you want you need to use the Arduino to switch relays that can handle the current.

user313: There are solid-state relays (such as this one) capable of switching the currents - 40A - you're talking about and may be a better choice than a mechanical one. Note that it will probably need to be mounted to a heat-sink.
You're Arduino then only needs to drive enough current to switch the relay. The example I gave above is not a recommendation as I've never used it; it's just the first one I found that is spec'd for enough more than 40 Amps to not be operating at its limit. I'm sure there are others as well.
The current it will draw from the Arduino is not specified; this is something you will need to find out about whatever relay you choose, to be sure it won't exceed the Arduino's 20 mA pin-driver spec. It is spec'd to require a heat sink. 

47552: <p>I am trying to make a cooler using Peltier Modules, the Peltier Modules and the fans switch on when the Temperature sensor attached to the circuit reads above a certain threshold. But I know that Arduino can only handle a couple of MilliAmps as its functionality, in such a case, how can I control my 480W circuitry (12V/40A) using Arduino? </p>

<p>I'm very new to all this and will appreciate a detailed answer.</p>

<p><strong>EDIT: To the best of my knowledge, this is not a duplicate of another question as the other question says <em>I'm currently working on several projects that each require controlling devices ranging from 800mA to 2A from an Arduino Uno.</em>, whereas my application requires much larger current than that.</strong></p>
 10394: <p>You are correct the Arduino can only handle a few mA at 5V.  In order to do what you want you need to use the Arduino to switch relays that can handle the current.</p>
 313: <p>There are solid-state relays (<a href="https://rads.stackoverflow.com/amzn/click/B00KO46YCU" rel="nofollow noreferrer">such as this one</a>) capable of switching the currents - 40A - you're talking about and may be a better choice than a mechanical one. Note that it will probably need to be mounted to a heat-sink.</p>

<p>You're Arduino then only needs to drive enough current to switch the relay. The example I gave above is not a recommendation as I've never used it; it's just the first one I found that is spec'd for enough more than 40 Amps to not be operating at its limit. I'm sure there are others as well.</p>

<p>The current it will draw from the Arduino is not specified; this is something you will need to find out about whatever relay you choose, to be sure it won't exceed the Arduino's 20 mA pin-driver spec. It <em>is</em> spec'd to require a heat sink. </p>
