Physical Attacks - Melee
Understanding Raiden's Move-Set is important to mastering him as a weapon. The first thing you'll notice after playing any time at all is that there are essentially three ways to damage an enemy with your HF Katana: Blade Mode, Wide Attacks and Strong Attacks.
While in Blade Mode, use the Right Stick to adjust the angle, and the Left Stick to change direction. Release the Right Stick to swing your sword in the current direction.
Parrying is key to mastering MGR, and you will most likely not be able to complete the game on higher difficulties without it. On Easy, parrying is done automatically for you, but on any other difficulty you'll have to do it yourself.
Incoming attacks can come from all directions (360 degrees) and are indicated by little red flashes. You'll need to press the left analog stick simultaneously with X (Xbox360) or Square (PS3) to parry, and the left analog stick must be pushed in the direction the attack is coming from. Most importantly, the left analog stick can NOT be held during this time (or you'd block perhaps one attack at most). You must release the left analog stick to it's initial position and press it again in the same or other direction to parry other attacks.
If you time all of this precisely before the enemy hit you, a parry can be performed on the slightly stunned enemy. Otherwise, Raiden will simply block the enemy attack, which usually works fine as well.
Not all attacks can be parried or blocked. Any attack where the enemy flashes yellow for a brief moment are such attacks, and you'll want to avoid them by running around with Ninja Run or by pressing X+A (Xbox 360) or Square+X (PS3) along with the left analog stick.