These modules, which LG calls 'Friends', really set the phone apart from others on the market - one external module, which is bound to be the most popular, is an external battery pack which doubles up as a dedicated camera controller.
Simply by pulling out the base and battery of the G5 and clipping the new module in, users will get an extra few hours of battery life and physical camera shutter and zoom buttons.
Another module, developed by Bang & Olufsen, is a Hi-Fi digital-to-analogue (DAC) converter, which promises to provide drastically improved audio quality when listening to music with headphones.
The easy-to-remove battery will also mean users can carry around a spare, swapping it out with the dead battery if they need another charge.
LG is working on more modules, and it's also opening the technology up to third-party manufacturers.
Most leading smartphones are completely sealed shut, and opportunities for hardware customisation are practically non-existent. It's a real change to see LG encouraging designers and users to tinker around with the G5 and create interesting new accessories.
There's a few more unusual features on the G5 - the phone has two rear cameras, one of which can be used to take 135-degree wide-angle shots. It also has an always-on display, like the Galaxy S7. You can see the phone's full specs on LG's website.
Following in Samsung's footsteps, LG is also releasing its own virtual reality headset, the LG 360 VR. Unlike the Samsung Gear VR, which uses a plugged-in smartphone as its display, the LG headset has its own built-in screens, which give higher-resolution images and allow the G5 to be used as a controller.
They've also launched a handheld 360-degree camera to go along with the camera.
The strangest accessory, however, is a small spherical robot, which users will be able to control via their smartphones. It's fitted with a camera, speakers and a laser pointer, and it's designed to let you keep an eye on the house or play with pets when you're not at home.
In a smartphone market dominated by relatively similar devices, LG has set itself apart with the G5. There's no news yet on the price or release date, but it's expected to hit the market in April.
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