The way you look is important in Spain and this fact is borne out by the way in which people dress for work. Styles of dress will vary from industry to industry with the more conservative professions of finance and the law favouring suits and ties and mainstream industry being somewhat less formal.
What is universally true, however, is that managers will invariably be very well-groomed wearing good quality, well-cut clothes.
The importance of appearance should not be taken underestimated - if you want to be respected look the part! This applies both in formal business settings and in more informal social situations.
As it can get very hot in the summer, do not arrive with heavy clothing in June - lightweight fabrics will make your visit much more comfortable.