If you have heard players like Joe Satriani or Alan Holdsworth, then you have witnessed truly breathtaking legato technique (better known as hammer-os and pull-offs). Having good legato technique will help balance out your picking technique. When you want that aggressive, in-your-face sound, then stick to your picking technique, but if you want to play smooth, and fluidly, then legato technique is what you want.
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Sometimes, you want to traverse a wide range of notes while just sticking with a string or two. To do that with fluid sounding legato technique, you need to throw in some slides so you can cover the distance. This exercise will teach you to do just that.
There are a variety of ways you can play this. You can do the slides with the first finger, the 4th finger, or both. Don't pay too much attention to how I wrote the Tab. Just get your fingers moving around til you get into a groove that works for you.