Malgalad's identity is difficult to ascertain for sure; our only reference to him is as the leader of the army of Lórien, who fought and died in the Battle of Dagorlad. This account is complicated by the fact that elsewhere the King of Lórien at this time is named as Amdír, who also led an army to the same War, and also died on Dagorlad. The simplest interpretation seems to be that Malgalad and Amdír are alternative names for the same individual; most likely Tolkien simply intended to change the name, though at a stretch we could take 'Malgalad' as a surname or title of KingAmdír.
An alternative interpretation would be that Amdír and Malgalad were actually different individuals. Malgalad is never specifically named as King of Lórien, so he may conceivably have been the captain or general in charge of Amdír's forces, who fell beside his King in battle. This does not seem especially likely (given that the account of Malgalad seems to place him in sole charge of the Elves of Lórien, with no mention of Amdír) but it is not entirely inconsistent with the relevant text.
We know that Amdír (Malgalad's presumed alter-ego) was of Sindarin extraction, so if the two names refer to the same character, then Malgalad was Sindarin too. However, in the less likely case that these were different individuals, it may be that Malgalad was one of the Silvan Elves ruled by Amdír.
The titles King and Lord of Lórien depend on Malgalad's identity with Amdír. If the two were separate individuals, these titles would not apply to Malgalad, though in that case he would still have been a military leader of some significance.