Been using the Shure SM 58 for some time without really thinking about it? Do you like it. It is common believe the SM 58 is quite good for vocals, robust microphone which sounds and feels good. True, but the microphone may also add a bit of brightness which you may not like at all times.
To change the tone of your microphone you may want to use EQ settings on your desk, but really the tone starts with your own voice and the tonality of the microphone. What about trying various microphones to see how they suit your voice?
If you have several microphones you may use for your bandpractise, why not use the SM 57 for voice? But it is a guitar microphone you may say. A micorphone does not mind what sound source it is amplifying, just try it and see what the results are. The only thing you need to be careful with is sensitive microphones: You do not want to damage them by putting them infront sound sources which cause sudden volumebursts as this could be harmful for that particular microphone.
When you try the SM 57 for vocals you may find it a tad smoother, maybe lacking some power (not as bright as the SM 58) but it may be just the ticket for your voice to tame that brightness.
You can even experiment with bassdrum microphones, some of them may be smooth and not having the treble the SM58 does have, they may also lack that bassboost when you sing close up into the microhone. Both the SM58 and 57 do have that ability, this is sometimes what you may like, other times you wish the microphone would preform in another way.
The point is, try to find out what works you by looking at what you like about the sound of your microphone.
In case you only have one microphone, try working with the EQ on your mixer (or use an external EQ), also look at reverbs and delay as they will also have an effect on the tone of your voice. Using some EQ and reverb may give you the ability to cover up some of the brigthness of a particular vocal microphone.
Keep experimenting and hope to catch you soon again,