ION Loaders are Loaders that have Tesla coils on their shoulders. They can charge these up, producing a barrier around them, making it so any bullets fired from the player will bounce off of it. Any enemies housed within the large dome shaped shield will be protected from your weapons but are capable of firing through the shield back at you. It is possible to pass through the shield and attack enemies while insid but you will get electrocuted and can suffer heavy damage, particularly to shields. When this heavy damage is paired with the damage dealt by the normal enemies usually housed inside, entering one of these shields is a very quick way to die.
In its normal form, ION Loaders shoot very powerful shock shots (similar to Repair Surveyors but more powerful) that can remove large amounts of shields. The combination of their shielding and the amount of damage they can deal should make these enemies the top priority whenever they appear on the field.