I really depends on whether you want the photo to be correctly exposed for the sun itself, or whether you want to correctly expose for a piece of sky that includes the sun.
In the first case you need to use a type of neutral density material to reduce the brightness of the sun to a level your camera can handle. The following image was made using a piece of welder's glass over the front of the lens. There are solar filters specifically designed to be used with telescopes and telephoto lenses when imaging the Sun.
Pointing an unprotected camera and lens directly at the sun when it is high in the sky can cause potentially cause damage to the camera (shutter curtains, sensor, light box, etc)and/or lens, especially when using high powered telephoto lenses. Looking at the sun through the viewfinder using an unprotected telephoto lens can cause permanent eye damage! Remember that even if you have a very narrow aperture selected, the lens stays wide open when composing, metering, and focusing! The aperture only stops down the instant before the shutter opens. For more, see How do I photograph the sunset without damaging my camera? and Is it dangerous to take pictures of the sun without any filter?
Canon EOS 7D and 70-200mm f/2.8L IS II at 120mm (with large piece of #12 welder's glass attached to the front of the lens). ISO 100, f/16, 1/1600 sec. Heavily cropped. The large dark spot is the planet Venus transiting the Sun on May 5, 2012. The lighter spots are sunspots. Note that the Sun was very high in the sky at the time and so of course the sky was very bright. But to get proper exposure of the sun itself the sky appears to be dark!
On the other hand, if you want to capture the surrounding sky then you must expose for the sky rather than the sun. With wider angle lenses the risks of pointing your camera at the sun are lower, but still very real. Unless the Sun is very close to the horizon, do so only long enough to capture the image and never look directly at the sun in your viewfinder! Always look at another area of the frame!
Canon EOS 5D Mark II and EF 70-200mm f/2.8 L IS II at 70mm. HDR image combining three frames. ISO 320, f/11, respective shutter speeds of 1/3200, 1/800, and 1/200 second for a -2, 0, +2 stop series.
Even in the dark frame the sun is completely oversaturated. In the brightest frame much of the center of the frame was blown out. Processed in Canon's Digital Photo Professional 3 with the same recipe applied to all three frames and the raw files combined using the HDR module of DPP 3 with additional adjustment made to brightness, saturation, contrast, detail enhancement, and smoothing.