Nothing improves your lead playing faster than soloing over a groove. Press play on any track below — it loops a chord progression with bass and click — then improvise using the suggested scale. Only one track plays at a time.
Before soloing, just play the root note of the key on every chord. Hear how it sits. Then add the rest of the scale.
Land on a note that's in the current chord when it changes — that's what makes a solo sound "right." See the improv page.
Don't play constantly. Rests make the notes you do play matter more. Phrase like you're having a conversation.