• Stainless Steel - The most commonly used material is stainless steel because of its resistance to rust and tarnishing. It is durable and can survive falls and dents. It is very easy to clean!
• Cast-Iron - This is my ultimate choice for the best cookware material to be found. These pieces last a lifetime. This is the best material to hold in the heat after it is removed from the stove. While unenameled bare cast-iron needs much care and cleaning to avoid tarnishing (though it will still last you a lifetime), most cast-iron pieces have enamel surrounding the iron which makes them extremely resistant to rust and other tarnishing. Try to be careful as the enamel can be chip-friendly if not handled appropriately. The rule of thumb is the higher the quality of the kettle, the better the enamel will stand up to chipping.
• Aluminum - This is inexpensive and very lightweight and is best for people who don't use the kettle more than once a day. It is very prone to tarnishing and limescale and rust - it is very important not to leave any water in the kettle when you are finished with it - wipe it dry every night. This material also loses heat very quickly, and so will the water that is in it.
• Copper - Stunning and a sure conversation starter, these kettles are beautiful pieces shaped out of shiny copper metal. They are some of the prettiest kettles out there. Copper is a serious conductor of heat, so your water will boil more rapidly, but it will also lose heat quickly once taken off the stove. Copper is prone to dents because of its soft material, and some polishing would be advised.
• Plastic - Although you can find some substantial plastic construction for kettles, it is best to avoid this material for kettles due to the potential problems it can create. Safety, for one, with melting. Health risks with chemicals in the plastic that leach into water when heat is used, and the hazardous BPA that is very harmful. No reason to worry about all this when there are so many other safe and more effective options out there!
• Glass - This is an attractive and useful material for kettles as it allows you to immediately see how much water is left and if it is boiling or not. Tempered glass is made to be used directly on a heat source. The only things to remember are to avoid extreme temperature changes (don't take a glass kettle from a boiling temperature and put it in the sink and pour cold water on it - it could shatter) and handle this with care - no rough handling - it is still glass! Glass will show limescale much more.
• Ceramic - Kettles made of ceramic are attractive and useful, very safe as there is no leaching of harmful chemicals into your water while it boils, no change in taste or smell of the water, either. Ceramic resists tarnishing and is easy to clean. Another bonus is that many ceramic kettle manufacturers also make matching sets with cups, sugar bowls, and cream pitchers.