In Super Nuke Bros. Melee, you have the option to shield against your opponents attacks! Whilst holding down the shield button, instead of taking damage, you will slide backwards slightly when hit.
The shields appear as colored bubbles.
If you press a direction while sheilding, you'll go into a roll. You are completely invincible during this roll, but you can be hit with a well timed attack coming out of it, so be careful!
Approach from behind, and attack.
Naturally, this means that you can't move while shielding, and there are other disadvantages as well. You can't shield forever, while you hold down the button, your shield gets smaller, and as you take hits, it gets smaller faster.
If you let it get small enough, the next attack you take will leave you stunned for a few seconds. We call this a Shield Break.
Perfect. Now that he's paralyzed, I'm in charge!
Keep in mind also that shields aren't indestructable, there are a few moves that can break your shield in one hit, so watch out for those.