Jesus summoned those whom he wanted and they came to him so  that they might be with him. The Gospel reading for today recounts the calling of the twelve apostles by Jesus, an event that is central to the mission of Jesus. Jesus not only chooses them for companionship, but he also bestows upon them the  authority to be partners with him in ministry. It is important for us to note that the summons to discipleship comes from Jesus himself. It  is an event of election, a free decision of the Lord. The twelve did not approach Jesus. There were no campaigns involved, no lobbying for the available positions, and there were no  resumes sent to Jesus by prospective candidates. Jesus simply picked those he wanted from those who were following him (they were already his disciples). In other words, he chose from those who were  available and had already committed to the cause. 
The calling/summoning of the twelve apostles introduces us to a very important aspect of discipleship: availability. I must be  with Jesus when he wants me. I must be  with Jesus to give him the opportunity to know me. I must be ready to let Jesus know me to the point of calling me  by name. All the three synoptic evangelists identify the twelve by their names. Yes, the twelve are part of a group now (they get to be collectively known as the twelve from here onwards), but they retain their individual identity. Jesus wants me as I am – my strengths as well as my weaknesses. During our baptism, we are called by name and baptized individually. Our baptism inserts us into the community of the faithful but we still retain our individual identities. For it is only thus that we can bring our unique gifts and talents and employ them at the service of the Church. The twelve became successful partners of Jesus because they brought with them their individual gifts and talents.