When picking up guitar, you can count yourself lucky that there are tutorials scattered around, and plenty of resources for you to take advantage of. Electric rock guitars are an iconic image of music, and one that can be a blast to play and are easy to pick up especially with the large amount of people that play them and the variety of tutorials and sheer amount of electric guitars that are on sale.
The first step of learning to play electric rock guitar, is choosing a guitar. There are many entry-level guitars that suit different genres of music. For instance, many name brands make excellent beginner guitars to play classic rock. They are entry-level guitars made by big name guitar manufacturers. To play metal specific guitar companies manufacture beginning level electric rock guitars that are priced accordingly for people just starting to get interested in the instrument.
Next, you will need an amp.
Electric guitars just aren't the same if you don't amplify them. Something small is best to start with, something hovering between 10 and 30 watts. This should not cost you more than one hundred dollars. Once you play for a while, you might want to move up to something that offers more effects, and more power. There are plenty of companies that make amps in this range. There are plenty of varieties to pick from, and most of them offer at least one model in the beginners range, at a budget price.
Then you will need picks, you will need lots of them. They get lost quickly and easily, no one ever avoids that problem. They are the size of a quarter and even thinner, and lighter, luckily they are cheaper accordingly. Electric rock guitars are played in many ways, and some people don't even use picks, some pick different sizes or thicknesses of picks. Ultimately, you just have to find what you are comfortable with.
Electric guitars need strings of quality, without good strings an electric guitar is worth nothing. Investing in good strings can lead to awe inspiring sound that you will be proud of; they also aren't very expensive. It is important to buy quality strings and while there are many brands which are quite common for use with electric guitars, and still fit a budget.
Next, you have to practice. The first step is learning tablature; there are many books on tablature as well as tutorials online. Learning tabs will help you read music, and play it more efficiently. You need to learn tablature, and you need to start playing regularly. Practice will lead you to talent and pretty soon, you and your electric guitar will be making beautiful music together.