NOTE: A hybrid mod is only for those who know exactly what they are doing, absolutely nothing for beginners!
A hybrid mod is a mode wherein the tank or the atomizer has direct contact with the battery, instead of first contact with a 510-pin (adjustable, floating, etc.). A hybrid is often shorter because they do not have a top cap with a 510-pin built in. However, they can be very dangerous! If you get a short circuit in your atomizers coil, many bad things can happen. For example, you might not be able to turn off the firing mechanism and the battery wont be able to ventilate itself properly, which could mean an implosion is about to happen. To reduce the risk that something similar will happen, you need an atomizer with a longer 510-threading, so long that it does not sit flush on the mod. It sits flush, there is a greater risk of short-circuiting.
If you get short, you’ll need to put the mod apart ASAP. The longer you wait, the warmer the mod will be. If you cant manage to dissemble it, put it in an area where people, animals or property are not nearby if it would implode. When you have gotten a short your battery is most likely fried, dispose it and replace it with a new one. Also, check the threading on your mod, the heat could have distorted them. If everything seems okay so you can use the mod again. But if you find any errors, get rid of it right away.
Always ask somebody who can help you with hybrid mods before buying one for yourself!
On the picture below we got a beautiful Manhattan V3 from US based Continuous Current, which is a hybrid mod. And in the video below Youtube profile "Suck My Mod" talks further about hybrid mods and safety.