OK the recipe for a smooth solo tone and to make an impact.
Your solo has to DOMINATE, there is nothing so pitiful as a solo that is getting drowned out by the band, whatever volume you were playing at before the lead break has to increase a lot when you are doing the widdly diddly stuff, you need a sound mixer that knows the songs or you need a second master volume (cranked) on your amp that is foot switchable. The second option is better because it injects more power amp gain that is going to give you a fatter smoother sound. The option of a switchable midi preamp as well as your tube amp can give you a whole swag of more solo tone options.
Next is a good delay to add the overtones that inject harmony and emotion to the solo.
Essential component (for parts of the solo, not the whole thing), speed, it adds exhilaration. Melody and unpredictability are also essential ingredients.
Some of my favourite solos that tick these boxes, Megadeth - A Tout le Monde, KISS - Deuce, Metallica - Enter Sandman, Thin Lizzy - The Black Rose, Vain - Secrets, Backyard Babies - Making Enemies is Good, LA Guns - I Wanna Be Your Man.