Good sound with an electric guitar has a lot to do with pickups and amplifiers. One is responsible for converting your playing into an electrical signal, and the other is responsible for amplifying that signal and shaping its tonal characteristics. The two can work together to create stunning tones and textures, and different combinations will produce very different results.
By far the two most common kinds of pickup, the single coil and the hum-bucker can both sound truly amazing with a tube amplifier. Single coils produce a little more background noise, as things like lighting can interfere with them, but they have a very full, warm tone which works great with tube distortions. Single coils in the neck are very rich and warm, but when placed at the bridge position they pick up on the sharper highs of the notes, and going through the tube amp can make a great attacking tone for guitar solos.
Hum-bucker pickups produce a lot less background noise, thanks to their hum cancelling opposite polarity design, and pass a much stronger signal on to the amplifier than a single coil pickup does. This means that it is a little easier to push a tube amplifier head into natural distortion with a hum-bucker. These kinds of pickups are a little darker and colder than the single coil design, and so tend to work best with high gain and distortion. Placed in the neck position they are a little warmer, but at the bridge position they really produce a gritty tone that is very useful for a lot of rock and metal.
With a good Tube or Valve amp setup and the right kinds of pickups, you can go from sweet clean backing and full, rich chords, all of the way through to darker metal riffing and solos, just by being aware of your volume, tone controls and pickup selection on your guitar itself. Of course, really great tones will involve effects pedals as well as the tube amplifier, but choosing appropriate pickups and amp heads for your sound is the best foundation to build a solid tone on!