Find band members who will form a cohesive unit. Start by asking around and seeing who is interested in forming a metal band. Also placing ads online or looking in metal forums are great ways to find talented musicians. You will need a singer with great stage presence, a guitarist and bassist capable of playing solid riffs and a drummer capable of playing fast. Also you will need to make sure everyone has the proper equipment for playing metal music.
Decide on the direction the band will go. For example, does the band want to play fast paced, thrash-type metal or slower, more melodic metal with plenty of breakdowns. Bands will usually find their own individual niche as time goes on but it is best to have a template to start with.
Pick a band name that fits what the band is all about. Most metal bands have very dark and morbid names, so choose accordingly.
Start practicing and get a feel for everyone's style. It takes time for musicians to properly mesh and learn to play with one another. The best way to begin this process is to just dive in and start playing.
Write original songs and keep practicing them until they become second nature. This process takes time and dedication but is a must for any serious metal band.
Record the band's music. Thanks to recent technology there are many cheap or free music recording software programs that can record professional quality audio. You could record this way or go the more traditional but expensive route of going to a studio.
Circulate your band's music. You can upload your music to websites online or pass out demos to get your name out. This is the process that must happen to get offers for playing shows and record deals.