Note: practice melee combat on a duel server.
In general, your arrow/asdw keys for movement. Mouse to aim. The controls can easily be changed in the settings. Normally you can hotkey the items/weapons too. Left click to swing your melee weapon. Rightclick for leap or block. More on leap and block later. Default for jump is spacebar.
Health bar: If this one gets to zero, you die. Important one. It's the big red one on the left. Humans have medkits. Beast has carnivorous, restores health upon hit. Officers radiate an aura that increase the health regeneration of themselves and nearby allies. Health always regenerates, just very slowly, but Rabid increases your health regeneration. Beast also has the replenish buff.
Stamina bar: Leaping, jumping and running takes stamina. It's the white bar on the right. It recharges over time. Beast has rabid to recharge stamina on every hit. It recharges faster above a certain point, so in melee its a good idea not to let it reach the bottom as it will take a long time to recharge
Xp bar: The blue bar on the right. There is a lvl indicator above it (the number). You get bonuses from being higher lvl till lvl 10. Bonuses are as follows:
Level 2: Increased Labour (You repair buildings faster and can carry 50 redstone and 50 gold)
Level 3: Small Armour (Your HP is increased)
Level 4: Increased Attack (Your melee attacks do slightly more damage)
Level 5: Increased Stamina (Your stamina bar is used up slower than normal)
Level 6: Medium Armour (Your HP is increased further)
Level 7 (Humans): Shield (A shield is gained to decrease the damage you take from a block)
Level 7 (Beasts): Improved Leap (Your max Stamina is increased)
Level 8: Crush Buildings (Your melee attacks do more damage to buildings - watch as the enemy commander starts to go into a blind panic!)
Level 9: Full Armour (Your HP is increased even more. You are now a combat god!)
Level 10: No more upgrades available. (Although something may happen as you level up more)
The general idea is to kill the enemy while taking minimal damage yourself. This can be achieved in several ways. Movement is an important aspect of Savage, certainly in melee combat. All non-siege units can evade enemy swings. Don't just stand there. Move. Sidestep. Avoid enemy swings while trying to make your swings hit the enemy. Beast can use leap to quickly get close to an enemy or to quickly get away from danger. You can also use sprint to close distances or to create distance. Stamina is precious, don't waste it. Certainly for beast. A beast without stamina can't leap and has little survival chances against skilled opponents.
In normal games, stealth or moving silently can be very important. Even a behemoth can sneak up to someone. Press both forward and backward movement keys at the same time to walk slowly, a behemoth does not shake the ground and does not make noise when he's slowwalking. Of course, you're still this big fat tree-wielding giant so they generally can see you, making the whole slowwalking behe pointless, but on some maps, sometimes, it can be very useful. Leaping, jumping, swinging... It all makes noise. If you're sneaking up on someone, try to avoid making noise. It's possible to kill an enemy very quickly, if you surprise him.
Try to be unpredictable. Try to confuse or trick the enemy. For example, make him think you'll attack him from the left and then go for his right. You don't have to constantly stare at the enemy. Certainly with legionnaires and predators, who have a pretty big swing, you can hit people on your left and right too. You can also quickly turn around, hitting multiple enemies with one strike. Or, as beast, leap around. Combined with rabid and enemies that don't block, a skilled beast player can take on more then ten enemies at the same time. He just leaps from target to target, hitting people as he flies by. If the humans don't block, the beast has infinite stamina and his only worry is avoiding the enemy swings, which can be achieved by moving around very quickly with leaping.
An interesting thing to know is that Predators and Legionnaires can not hit things that are very close to them. So if you're fighting, for example, scavenger versus legionnaire, the scavenger can hit the legionnaire he's bumping into, but the lego can't hit the scavenger hugging him.
There are training videos available that help explain movement in melee combat. There are also special duels servers, where people do nothing but melee 1 vs 1 duels. If you ask politely, you might get one of them to train you. Some moves have names, such as bounce and backstab.
Some sort of jump. Requires stamina. Is one of the most important things for a beast. With leaps you can attack an enemy from behind and front for example in a very short time span. You can fake leaping for the left and change direction in midair. You can leap in any direction. (backwards, left, right, front) Your leap is at it's best at lvl 7 and up. For a very good guide on the basics of beast meleeing, (specifically with Predators) watch the following video.
Basicly stops an enemy melee attack and stuns them for a short amount of time. Very important for humans. It decreases the damage you would get from the hit too. Your block is at it's best at lvl 7 and up. You can block all damage, except the damage over time from being poisoned. You can´t move and block at the same time unless you are jumping.
Beast: Only use run to get uphill. Leap is better for dodging attacks, but you cant leap uphill. This should be the only time you have to use sprint on beasts. If you use it otherwise it would be a waste of your stamina, although it can be used as a last-ditch effort to get away from the deadly swing.
Human: Useful. Use it to quickly step aside so the beast his leap misses you. Can be combined with hitting the beast as it flies by. When they leap, they usually land some distance away, you can use the run to quickly catch up with them, give them a few swings and mess up whatever leap plan they had in mind next. Generally speaking, if you stand still, you'll become a splat in the wall in no time. The stamina is there to be used, after all!
Can be used to gain speed when going down hill. Can be combined with leap. It does take stamina so use it with care. If you, as human, go up a slope and beast follows you, can jump down behind them and hack em up. Leap first, then jump to keep yourself going for a bit longer (that is called a bounce).