For the digital photographer especially batteries are more important than film. After all they are likely to run out first!
This makes battery selection a crucial topic.
There are several types...
Do not use rechargeable batteries in your camera. Use standard, Alkaline (or lithium) only. The voltage is lower, and this can throw off your meter!
Some modern batteries have energy densities close to that of Dynamite, and pose a severe fire hazard if accidentally short-circuited.