In Act 1 Scene 1, Antonio is presented as:
* Melancholy and introspective: He is described as "sad" and "unfortunate" by others, and he himself says he feels a "heavy heart" and is "not in a merry vein." He is even worried about the possibility of death.
* Generous and thoughtful: He is deeply concerned for his friend Bassanio, willing to lend him a large sum of money and even risk his life for his friend's happiness.
* A successful merchant: Despite his melancholy, Antonio is depicted as a wealthy and respected merchant, capable of providing a significant loan.
* Haunted by past experience: While the exact nature of his melancholy isn't explicitly stated, it's suggested that past experiences, perhaps financial losses or a past romantic disappointment, contribute to his somber mood.
* Suspicious of love and relationships: He expresses doubt about the motives of those who seek to marry for love, suggesting he may have experienced a painful relationship in the past.
While the exact reasons for his melancholy remain somewhat mysterious in Act 1 Scene 1, his overall character is established as a thoughtful, generous, and somewhat troubled figure.