What works for me is to get the riffs under control first. The “creative” process is a case of just playing bits and pieces and experimenting. The trick is to have a cassette recorder going so that you can go back through what you’ve done to see if there is anything worth developing. As for words, well, have you seen the number of AC/DC or Death Metal lyrics on the mis-heard lyrics sites.
There’s a Metal Song Title Generator at http://www.returntothepit.com/bullshit.html which is fun even if you don’t use any of the titles it generates.
